diff --git a/executable_semantics/ast/expression.cpp b/executable_semantics/ast/expression.cpp
index 3d64f069f3218..07a728cdea262 100644
--- a/executable_semantics/ast/expression.cpp
+++ b/executable_semantics/ast/expression.cpp
@@ -271,7 +271,7 @@ void Expression::Print(llvm::raw_ostream& out) const {
       out << "Bool";
       break;
     case ExpressionKind::IntTypeLiteral:
-      out << "Int";
+      out << "i32";
       break;
     case ExpressionKind::TypeTypeLiteral:
       out << "Type";
diff --git a/executable_semantics/interpreter/value.cpp b/executable_semantics/interpreter/value.cpp
index 8afd86b1944de..3faaab09271f0 100644
--- a/executable_semantics/interpreter/value.cpp
+++ b/executable_semantics/interpreter/value.cpp
@@ -192,7 +192,7 @@ void Value::Print(llvm::raw_ostream& out) const {
       out << "Bool";
       break;
     case Value::Kind::IntType:
-      out << "Int";
+      out << "i32";
       break;
     case Value::Kind::TypeType:
       out << "Type";
diff --git a/executable_semantics/syntax/lexer.lpp b/executable_semantics/syntax/lexer.lpp
index cd9358b6b669e..1da3d96e56a03 100644
--- a/executable_semantics/syntax/lexer.lpp
+++ b/executable_semantics/syntax/lexer.lpp
@@ -8,6 +8,7 @@ SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #include <cstdlib>
 #include <iostream>
 
+#include "common/check.h"
 #include "executable_semantics/common/tracing_flag.h"
 #include "executable_semantics/syntax/parse_and_lex_context.h"
 #include "llvm/ADT/StringExtras.h"
@@ -45,7 +46,6 @@ FALSE             "false"
 FN                "fn"
 FNTY              "fnty"
 IF                "if"
-INT               "Int"
 MATCH             "match"
 NOT               "not"
 OR                "or"
@@ -62,6 +62,7 @@ AWAIT             "__await"
 UNDERSCORE        "_"
 
 identifier    [A-Za-z_][A-Za-z0-9_]*
+sized_type_literal [iuf][1-9][0-9]*
 integer_literal   [0-9]+
 horizontal_whitespace [ \t\r]
 whitespace [ \t\r\n]
@@ -106,7 +107,6 @@ operand_start [(A-Za-z0-9_"]
 {FN}       { return Carbon::Parser::make_FN(context.current_token_position); }
 {FNTY}     { return Carbon::Parser::make_FNTY(context.current_token_position); }
 {IF}       { return Carbon::Parser::make_IF(context.current_token_position); }
-{INT}      { return Carbon::Parser::make_INT(context.current_token_position); }
 {MATCH}    { return Carbon::Parser::make_MATCH(context.current_token_position); }
 {NOT}      { return Carbon::Parser::make_NOT(context.current_token_position); }
 {OR}       { return Carbon::Parser::make_OR(context.current_token_position); }
@@ -122,6 +122,8 @@ operand_start [(A-Za-z0-9_"]
 {AWAIT}    { return Carbon::Parser::make_AWAIT(context.current_token_position); }
 {UNDERSCORE}      { return Carbon::Parser::make_UNDERSCORE(context.current_token_position); }
 
+{sized_type_literal} { return Carbon::Parser::make_sized_type_literal(yytext, context.current_token_position); }
+
 "=" return Carbon::Parser::make_EQUAL(context.current_token_position);
 "-" return Carbon::Parser::make_MINUS(context.current_token_position);
 "+" return Carbon::Parser::make_PLUS(context.current_token_position);
@@ -183,8 +185,9 @@ operator and its operand, leading to three more cases:
 
 {integer_literal} {
   BEGIN(AFTER_OPERAND);
-  auto r = atof(yytext);
-  return Carbon::Parser::make_integer_literal(r, context.current_token_position);
+  int val;
+  CHECK(llvm::to_integer(yytext, val));
+  return Carbon::Parser::make_integer_literal(val, context.current_token_position);
 }
 
 {ONE_LINE_COMMENT} {
diff --git a/executable_semantics/syntax/parser.ypp b/executable_semantics/syntax/parser.ypp
index 440eaf8a7f1b2..ac8d32c26bafb 100644
--- a/executable_semantics/syntax/parser.ypp
+++ b/executable_semantics/syntax/parser.ypp
@@ -55,8 +55,10 @@
 #include <list>
 #include <vector>
 
+#include "common/check.h"
 #include "executable_semantics/syntax/syntax_helpers.h"
 #include "executable_semantics/syntax/parse_and_lex_context.h"
+#include "llvm/ADT/StringExtras.h"
 }  // %code top
 
 %code requires {
@@ -88,6 +90,7 @@ void Carbon::Parser::error(const location_type&, const std::string& message) {
 
 %token <int> integer_literal
 %token <std::string> identifier
+%token <std::string> sized_type_literal
 %type <std::string> designator
 %type <Declaration> declaration
 %type <FunctionDefinition> function_declaration
@@ -129,7 +132,6 @@ void Carbon::Parser::error(const location_type&, const std::string& message) {
 %token AND
 %token OR
 %token NOT
-%token INT
 %token BOOL
 %token TYPE
 %token FN
@@ -221,8 +223,13 @@ expression:
     { $$ = Expression::MakeBoolLiteral(yylineno, true); }
 | FALSE
     { $$ = Expression::MakeBoolLiteral(yylineno, false); }
-| INT
-    { $$ = Expression::MakeIntTypeLiteral(yylineno); }
+| sized_type_literal
+    {
+      int val;
+      CHECK(llvm::to_integer(llvm::StringRef($1).substr(1), val));
+      CHECK($1[0] == 'i' && val == 32)  << "Only i32 is supported for now: " << $1;
+      $$ = Expression::MakeIntTypeLiteral(yylineno);
+    }
 | BOOL
     { $$ = Expression::MakeBoolTypeLiteral(yylineno); }
 | TYPE
diff --git a/executable_semantics/testdata/assignment_copy1.carbon b/executable_semantics/testdata/assignment_copy1.carbon
index d3f69431ad25a..5b8e663d0bc7b 100644
--- a/executable_semantics/testdata/assignment_copy1.carbon
+++ b/executable_semantics/testdata/assignment_copy1.carbon
@@ -4,10 +4,10 @@
 
 // Test that assignment performs a copy and does not create an alias.
 
-fn main() -> Int {
-  var x: Int = -1;
+fn main() -> i32 {
+  var x: i32 = -1;
   {
-     var y: Int = 0;
+     var y: i32 = 0;
      x = y;
      // y dies here
   }
diff --git a/executable_semantics/testdata/assignment_copy2.carbon b/executable_semantics/testdata/assignment_copy2.carbon
index b87125101b8fc..6507d38a47187 100644
--- a/executable_semantics/testdata/assignment_copy2.carbon
+++ b/executable_semantics/testdata/assignment_copy2.carbon
@@ -4,9 +4,9 @@
 
 // Test that assignment performs a copy and does not create an alias.
 
-fn main() -> Int {
-  var x: Int = 0;
-  var y: Int = x;
+fn main() -> i32 {
+  var x: i32 = 0;
+  var y: i32 = x;
   x = 1;
   return y;
 }
diff --git a/executable_semantics/testdata/block1.carbon b/executable_semantics/testdata/block1.carbon
index 40e9ae99ffe17..83cd1cfb24b34 100644
--- a/executable_semantics/testdata/block1.carbon
+++ b/executable_semantics/testdata/block1.carbon
@@ -2,10 +2,10 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
-  var x: Int = 0;
+fn main() -> i32 {
+  var x: i32 = 0;
   {
-    var x: Int = 1;
+    var x: i32 = 1;
   }
   return x;
 }
diff --git a/executable_semantics/testdata/block2.carbon b/executable_semantics/testdata/block2.carbon
index 4f0b10bf0f7d8..4e8f3c1819981 100644
--- a/executable_semantics/testdata/block2.carbon
+++ b/executable_semantics/testdata/block2.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
-  var x: Int = 0;
+fn main() -> i32 {
+  var x: i32 = 0;
   {
     // empty block
   }
diff --git a/executable_semantics/testdata/break1.carbon b/executable_semantics/testdata/break1.carbon
index 16db5182c3d0a..fbb844887bd4e 100644
--- a/executable_semantics/testdata/break1.carbon
+++ b/executable_semantics/testdata/break1.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
-  var x: Int = 2;
+fn main() -> i32 {
+  var x: i32 = 2;
   while (true) {
     if (x == 0) {
       break;
diff --git a/executable_semantics/testdata/choice1.carbon b/executable_semantics/testdata/choice1.carbon
index 4518955ba42c6..0ea54952e6d0c 100644
--- a/executable_semantics/testdata/choice1.carbon
+++ b/executable_semantics/testdata/choice1.carbon
@@ -4,11 +4,11 @@
 
 choice Ints {
   None,
-  One(Int),
-  Two(Int,Int)
+  One(i32),
+  Two(i32,i32)
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   var x: auto = Ints.None();
   var y: auto = Ints.One(42);
   var n: auto = 0;
@@ -34,6 +34,6 @@ fn main() -> Int {
 // Test some alternate syntaxes
 choice MoreInts {
   None(),
-  One(Int),
-  Two(Int,Int),
+  One(i32),
+  Two(i32,i32),
 }
diff --git a/executable_semantics/testdata/continue1.carbon b/executable_semantics/testdata/continue1.carbon
index 317ddbc6df719..bca3143537b6e 100644
--- a/executable_semantics/testdata/continue1.carbon
+++ b/executable_semantics/testdata/continue1.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   var x: auto = 2;
   while (not (x == 0)) {
     x = x - 1;
diff --git a/executable_semantics/testdata/experimental_continuation1.carbon b/executable_semantics/testdata/experimental_continuation1.carbon
index 09c20178b60bb..003467591f6a6 100644
--- a/executable_semantics/testdata/experimental_continuation1.carbon
+++ b/executable_semantics/testdata/experimental_continuation1.carbon
@@ -4,8 +4,8 @@
 
 // Test that creating a continuation doesn't do anything.
 
-fn main() -> Int {
-  var x: Int = 0;
+fn main() -> i32 {
+  var x: i32 = 0;
   __continuation k {
     x = x + 1;
   }
diff --git a/executable_semantics/testdata/experimental_continuation2.carbon b/executable_semantics/testdata/experimental_continuation2.carbon
index d8f6baf6c5bdc..c60f9341af991 100644
--- a/executable_semantics/testdata/experimental_continuation2.carbon
+++ b/executable_semantics/testdata/experimental_continuation2.carbon
@@ -4,8 +4,8 @@
 
 // Test creating and running a continuation.
 
-fn main() -> Int {
-  var x: Int = 0;
+fn main() -> i32 {
+  var x: i32 = 0;
   __continuation k {
     x = x + 1;
   }
diff --git a/executable_semantics/testdata/experimental_continuation3.carbon b/executable_semantics/testdata/experimental_continuation3.carbon
index afcb180a7a1af..e11178f20df88 100644
--- a/executable_semantics/testdata/experimental_continuation3.carbon
+++ b/executable_semantics/testdata/experimental_continuation3.carbon
@@ -5,8 +5,8 @@
 // Test pausing a continuation with `__await` and restarting it with
 // `__run`.
 
-fn main() -> Int {
-  var x: Int = 0;
+fn main() -> i32 {
+  var x: i32 = 0;
   __continuation k {
     x = x + 1;
     __await;
diff --git a/executable_semantics/testdata/experimental_continuation4.carbon b/executable_semantics/testdata/experimental_continuation4.carbon
index f03df692a62c7..6f0ce7d51b8e2 100644
--- a/executable_semantics/testdata/experimental_continuation4.carbon
+++ b/executable_semantics/testdata/experimental_continuation4.carbon
@@ -5,8 +5,8 @@
 // Assignment for continuations is shallow, so `k2` refers to the same
 // continuation as `k1`.
 
-fn main() -> Int {
-  var x: Int = 0;
+fn main() -> i32 {
+  var x: i32 = 0;
   __continuation k1 {
     x = x + 1;
     __await;
diff --git a/executable_semantics/testdata/experimental_continuation5.carbon b/executable_semantics/testdata/experimental_continuation5.carbon
index efdb383202241..02c826ce827ed 100644
--- a/executable_semantics/testdata/experimental_continuation5.carbon
+++ b/executable_semantics/testdata/experimental_continuation5.carbon
@@ -4,10 +4,10 @@
 
 // Test access to block-scoped variables upon resuming a continuation.
 
-fn main() -> Int {
-  var y: Int = 0;
+fn main() -> i32 {
+  var y: i32 = 0;
   __continuation k {
-    var x: Int = 0;
+    var x: i32 = 0;
     x = x + 1;
     __await;
     x = x + 2;
diff --git a/executable_semantics/testdata/experimental_continuation6.carbon b/executable_semantics/testdata/experimental_continuation6.carbon
index 65f9cd07deb5e..e31592c94d150 100644
--- a/executable_semantics/testdata/experimental_continuation6.carbon
+++ b/executable_semantics/testdata/experimental_continuation6.carbon
@@ -4,9 +4,9 @@
 
 // Test recursive functions inside continuations.
 
-var current: Int = 0;
+var current: i32 = 0;
 
-fn CountUpTo(x: Int) -> Int {
+fn CountUpTo(x: i32) -> i32 {
   if (x == 0) {
     current = 0;
     __await;
@@ -18,12 +18,12 @@ fn CountUpTo(x: Int) -> Int {
   }
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   __continuation k {
     CountUpTo(5);
   }
-  var sum: Int = 0;
-  var count: Int = 5;
+  var sum: i32 = 0;
+  var count: i32 = 5;
   while (not (count == 0)) {
     __run k;
     sum = sum + current;
diff --git a/executable_semantics/testdata/experimental_continuation7.carbon b/executable_semantics/testdata/experimental_continuation7.carbon
index 597b2ce004cf8..9ada4c5a5cb98 100644
--- a/executable_semantics/testdata/experimental_continuation7.carbon
+++ b/executable_semantics/testdata/experimental_continuation7.carbon
@@ -6,11 +6,11 @@
 // on the stack such as the variable `x`. In this example the copy
 // happens after the variable `x` is created.
 
-var y: Int = 0;
+var y: i32 = 0;
 
-fn main() -> Int {
+fn main() -> i32 {
   __continuation k1 {
-    var x: Int = 0;
+    var x: i32 = 0;
     x = x + 1;
     __await;
     x = x + 2;
diff --git a/executable_semantics/testdata/experimental_continuation8.carbon b/executable_semantics/testdata/experimental_continuation8.carbon
index 6cb879a83c93d..d37bfe9b5e152 100644
--- a/executable_semantics/testdata/experimental_continuation8.carbon
+++ b/executable_semantics/testdata/experimental_continuation8.carbon
@@ -7,11 +7,11 @@
 // happens before the variable `x` is created, so each continuation
 // creates a different `x`.
 
-var y: Int = 0;
+var y: i32 = 0;
 
-fn main() -> Int {
+fn main() -> i32 {
   __continuation k1 {
-    var x: Int = 0;
+    var x: i32 = 0;
     x = x + 1;
     __await;
     y = x;
diff --git a/executable_semantics/testdata/experimental_continuation9.carbon b/executable_semantics/testdata/experimental_continuation9.carbon
index be705ef4240df..5cbba38d43f1f 100644
--- a/executable_semantics/testdata/experimental_continuation9.carbon
+++ b/executable_semantics/testdata/experimental_continuation9.carbon
@@ -7,14 +7,14 @@
 // is dangerous and can happen inside continuations.
 
 fn capture() -> __Continuation {
-  var x: Int = 1;
+  var x: i32 = 1;
   __continuation k {
-    var y: Int = x;
+    var y: i32 = x;
   }
   return k;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   var k: __Continuation = capture();
   __run k; // error, lifetime of x is over
   return 0;
diff --git a/executable_semantics/testdata/fun1.carbon b/executable_semantics/testdata/fun1.carbon
index 6016c2d336abe..c9b53d8891aba 100644
--- a/executable_semantics/testdata/fun1.carbon
+++ b/executable_semantics/testdata/fun1.carbon
@@ -2,10 +2,10 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn f(x: Int) -> Int {
+fn f(x: i32) -> i32 {
   return x - 1;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return f(1);
 }
diff --git a/executable_semantics/testdata/fun2.carbon b/executable_semantics/testdata/fun2.carbon
index a2980f353280b..f89949c2dd0cf 100644
--- a/executable_semantics/testdata/fun2.carbon
+++ b/executable_semantics/testdata/fun2.carbon
@@ -6,12 +6,12 @@
 // This makes sure that when the value in `x` dies,
 // it does not cause the value in `a` to also die.
 
-fn f(x: Int) -> Int {
+fn f(x: i32) -> i32 {
   return 0;
 }
 
-fn main() -> Int {
-  var a: Int = 0; var b: Int = 1;
+fn main() -> i32 {
+  var a: i32 = 0; var b: i32 = 1;
   f(a);
   b = a;
   return b;
diff --git a/executable_semantics/testdata/fun3.carbon b/executable_semantics/testdata/fun3.carbon
index 200570bb6babe..e8997e87c3c42 100644
--- a/executable_semantics/testdata/fun3.carbon
+++ b/executable_semantics/testdata/fun3.carbon
@@ -3,10 +3,10 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 // Test multiple arguments
-fn f(x: Int, y: Int) -> Int {
+fn f(x: i32, y: i32) -> i32 {
   return x + y;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return f(2,3) - 5;
 }
diff --git a/executable_semantics/testdata/fun4.carbon b/executable_semantics/testdata/fun4.carbon
index fffd1288b3591..9e38cd98dbdc4 100644
--- a/executable_semantics/testdata/fun4.carbon
+++ b/executable_semantics/testdata/fun4.carbon
@@ -5,7 +5,7 @@
 // Test empty parameters and return type
 fn f() { }
 
-fn main() -> Int {
+fn main() -> i32 {
   f();
   return 0;
 }
diff --git a/executable_semantics/testdata/fun5.carbon b/executable_semantics/testdata/fun5.carbon
index ad6bc85e870a6..1f392b6606830 100644
--- a/executable_semantics/testdata/fun5.carbon
+++ b/executable_semantics/testdata/fun5.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn add(x: Int, y: Int) => x + y;
+fn add(x: i32, y: i32) => x + y;
 
-fn main() -> Int {
+fn main() -> i32 {
   return add(1, 2) - 3;
 }
diff --git a/executable_semantics/testdata/fun6_fail_type.carbon b/executable_semantics/testdata/fun6_fail_type.carbon
index c2de7341cbbca..1576f5fb3c043 100644
--- a/executable_semantics/testdata/fun6_fail_type.carbon
+++ b/executable_semantics/testdata/fun6_fail_type.carbon
@@ -2,10 +2,10 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn f(x: Int, y: Int) -> Int { return x + y; }
+fn f(x: i32, y: i32) -> i32 { return x + y; }
 
-fn main() -> Int {
-  var xy: (Int, Int) = (1, 2);
+fn main() -> i32 {
+  var xy: (i32, i32) = (1, 2);
   // should fail to type-check
   return f(xy);
 }
diff --git a/executable_semantics/testdata/fun6_fail_type.golden b/executable_semantics/testdata/fun6_fail_type.golden
index 0bfd7543f597c..6182f1b903797 100644
--- a/executable_semantics/testdata/fun6_fail_type.golden
+++ b/executable_semantics/testdata/fun6_fail_type.golden
@@ -1,4 +1,4 @@
 COMPILATION ERROR: 10: type error in call
-expected: (0 = Int, 1 = Int)
-actual: (0 = (0 = Int, 1 = Int))
+expected: (0 = i32, 1 = i32)
+actual: (0 = (0 = i32, 1 = i32))
 EXIT CODE: 255
diff --git a/executable_semantics/testdata/fun_named_params.carbon b/executable_semantics/testdata/fun_named_params.carbon
index bb5d158a7267e..f9b627c987c24 100644
--- a/executable_semantics/testdata/fun_named_params.carbon
+++ b/executable_semantics/testdata/fun_named_params.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn f(x: Int, .d = y: Int) => x + y;
+fn f(x: i32, .d = y: i32) => x + y;
 
-fn main() -> Int {
+fn main() -> i32 {
   return f(1, .d = 2) - 3;
 }
diff --git a/executable_semantics/testdata/fun_named_params2.carbon b/executable_semantics/testdata/fun_named_params2.carbon
index 61b9952a35424..fe4911e627288 100644
--- a/executable_semantics/testdata/fun_named_params2.carbon
+++ b/executable_semantics/testdata/fun_named_params2.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn f(x: Int, .d = y: Int, z: Int, .e = a: Int) => (x + y) - (z + a);
+fn f(x: i32, .d = y: i32, z: i32, .e = a: i32) => (x + y) - (z + a);
 
-fn main() -> Int {
+fn main() -> i32 {
   return 0;
 }
diff --git a/executable_semantics/testdata/fun_recur.carbon b/executable_semantics/testdata/fun_recur.carbon
index c93318e182cb5..13a3924a631b8 100644
--- a/executable_semantics/testdata/fun_recur.carbon
+++ b/executable_semantics/testdata/fun_recur.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn f(x: Int) -> Int {
+fn f(x: i32) -> i32 {
   if (x == 0) {
     return x;
   } else {
@@ -10,6 +10,6 @@ fn f(x: Int) -> Int {
   }
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return f(2);
 }
diff --git a/executable_semantics/testdata/funptr1.carbon b/executable_semantics/testdata/funptr1.carbon
index 2173e0b6ff73c..8d7815a8c2e06 100644
--- a/executable_semantics/testdata/funptr1.carbon
+++ b/executable_semantics/testdata/funptr1.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn add1(x: Int) -> Int {
+fn add1(x: i32) -> i32 {
   return x + 1;
 }
 
-fn main() -> Int {
-  var f: fnty(Int)->Int = add1;
+fn main() -> i32 {
+  var f: fnty(i32)->i32 = add1;
   return f(-1);
 }
diff --git a/executable_semantics/testdata/generic_function1.carbon b/executable_semantics/testdata/generic_function1.carbon
index 3de4aba8bfeea..c49619d30fe7b 100644
--- a/executable_semantics/testdata/generic_function1.carbon
+++ b/executable_semantics/testdata/generic_function1.carbon
@@ -6,6 +6,6 @@ fn id[T:! Type](x: T) -> T {
   return x;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return id(0);
 }
diff --git a/executable_semantics/testdata/generic_function2.carbon b/executable_semantics/testdata/generic_function2.carbon
index ef782e367647d..556b8ebd15172 100644
--- a/executable_semantics/testdata/generic_function2.carbon
+++ b/executable_semantics/testdata/generic_function2.carbon
@@ -6,6 +6,6 @@ fn fst[T:! Type](x: T, y: T) -> T {
   return x;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return fst(0, 1);
 }
diff --git a/executable_semantics/testdata/generic_function3.carbon b/executable_semantics/testdata/generic_function3.carbon
index 716139ef58dca..d73579902de1d 100644
--- a/executable_semantics/testdata/generic_function3.carbon
+++ b/executable_semantics/testdata/generic_function3.carbon
@@ -2,10 +2,10 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn snd[T:! Type](x: Int, y: T) -> T {
+fn snd[T:! Type](x: i32, y: T) -> T {
   return y;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return snd(0, 1);
 }
diff --git a/executable_semantics/testdata/generic_function_apply.carbon b/executable_semantics/testdata/generic_function_apply.carbon
index d88324ab34c71..ad69b7012f8c9 100644
--- a/executable_semantics/testdata/generic_function_apply.carbon
+++ b/executable_semantics/testdata/generic_function_apply.carbon
@@ -6,7 +6,7 @@ fn apply[T:! Type, U:! Type](f: fnty (T) -> U, x: T) -> U {
   return f(x);
 }
 
-fn positive(x: Bool) -> Int {
+fn positive(x: Bool) -> i32 {
   if (x) {
     return 2;
   } else {
@@ -14,6 +14,6 @@ fn positive(x: Bool) -> Int {
   }
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return apply(positive, false);
 }
diff --git a/executable_semantics/testdata/generic_function_fail1.carbon b/executable_semantics/testdata/generic_function_fail1.carbon
index a21596bc4d983..0c3a19f67d578 100644
--- a/executable_semantics/testdata/generic_function_fail1.carbon
+++ b/executable_semantics/testdata/generic_function_fail1.carbon
@@ -6,6 +6,6 @@ fn fst[T:! Type](x: T, y: T) -> T {
   return x;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return fst(0, true);
 }
diff --git a/executable_semantics/testdata/generic_function_fail1.golden b/executable_semantics/testdata/generic_function_fail1.golden
index 95d8c5ec6c97c..c3d6a6dc1ca63 100644
--- a/executable_semantics/testdata/generic_function_fail1.golden
+++ b/executable_semantics/testdata/generic_function_fail1.golden
@@ -1,4 +1,4 @@
 COMPILATION ERROR: 10: type error in argument deduction
-expected: Int
+expected: i32
 actual: Bool
 EXIT CODE: 255
diff --git a/executable_semantics/testdata/generic_function_fail2.carbon b/executable_semantics/testdata/generic_function_fail2.carbon
index 690254d5d8da0..416ac52ae7df7 100644
--- a/executable_semantics/testdata/generic_function_fail2.carbon
+++ b/executable_semantics/testdata/generic_function_fail2.carbon
@@ -2,10 +2,10 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn id[T:! Type](x: Int) -> Int {
+fn id[T:! Type](x: i32) -> i32 {
   return x;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return id(0);
 }
diff --git a/executable_semantics/testdata/generic_function_fail3.carbon b/executable_semantics/testdata/generic_function_fail3.carbon
index dedbc94b13410..3b4ec683a592e 100644
--- a/executable_semantics/testdata/generic_function_fail3.carbon
+++ b/executable_semantics/testdata/generic_function_fail3.carbon
@@ -6,6 +6,6 @@ fn id[T:! Type](x: T) -> T {
   return x + 0;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return id(0);
 }
diff --git a/executable_semantics/testdata/generic_function_fail3.golden b/executable_semantics/testdata/generic_function_fail3.golden
index 7736dbc51630f..e39634c5ccdd1 100644
--- a/executable_semantics/testdata/generic_function_fail3.golden
+++ b/executable_semantics/testdata/generic_function_fail3.golden
@@ -1,4 +1,4 @@
 COMPILATION ERROR: 6: type error in addition(1)
-expected: Int
+expected: i32
 actual: T
 EXIT CODE: 255
diff --git a/executable_semantics/testdata/generic_function_swap.carbon b/executable_semantics/testdata/generic_function_swap.carbon
index b646b4a041f32..4a7bc419fb33a 100644
--- a/executable_semantics/testdata/generic_function_swap.carbon
+++ b/executable_semantics/testdata/generic_function_swap.carbon
@@ -6,6 +6,6 @@ fn swap[T:! Type, U:! Type](tuple: (T, U)) -> (U, T) {
   return (tuple[1], tuple[0]);
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return swap((0, true))[1];
 }
diff --git a/executable_semantics/testdata/generic_function_tuple_map.carbon b/executable_semantics/testdata/generic_function_tuple_map.carbon
index cd099cbd544db..e73084e2ca378 100644
--- a/executable_semantics/testdata/generic_function_tuple_map.carbon
+++ b/executable_semantics/testdata/generic_function_tuple_map.carbon
@@ -6,8 +6,8 @@ fn map[T:! Type](f: fnty (T) -> T, tuple: (T, T)) -> (T, T) {
   return (f(tuple[0]), f(tuple[1]));
 }
 
-fn inc(x: Int) -> Int { return x + 1; }
+fn inc(x: i32) -> i32 { return x + 1; }
 
-fn main() -> Int {
+fn main() -> i32 {
   return map(inc, (0, 2))[0];
 }
diff --git a/executable_semantics/testdata/global_variable1.carbon b/executable_semantics/testdata/global_variable1.carbon
index ee13c7c9bd819..59c9863880afc 100644
--- a/executable_semantics/testdata/global_variable1.carbon
+++ b/executable_semantics/testdata/global_variable1.carbon
@@ -4,8 +4,8 @@
 
 // Test global variable initialization and read.
 
-var zero: Int = 0;
+var zero: i32 = 0;
 
-fn main() -> Int {
+fn main() -> i32 {
   return zero;
 }
diff --git a/executable_semantics/testdata/global_variable2.carbon b/executable_semantics/testdata/global_variable2.carbon
index 22da34ad97fad..976c7ffc77d88 100644
--- a/executable_semantics/testdata/global_variable2.carbon
+++ b/executable_semantics/testdata/global_variable2.carbon
@@ -5,13 +5,13 @@
 // Test that mutations to a global variable in one function is visible
 // in another function.
 
-var flag: Int = 1;
+var flag: i32 = 1;
 
 fn flipFlag() -> () {
   flag = 0;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   flipFlag();
   return flag;
 }
diff --git a/executable_semantics/testdata/global_variable3.carbon b/executable_semantics/testdata/global_variable3.carbon
index 0bff693af229b..3fd83e2c3b8dd 100644
--- a/executable_semantics/testdata/global_variable3.carbon
+++ b/executable_semantics/testdata/global_variable3.carbon
@@ -4,8 +4,8 @@
 
 // Test type checking of global variable. Error expected.
 
-var flag: Int = true;
+var flag: i32 = true;
 
-fn main() -> Int {
+fn main() -> i32 {
   return 0;
 }
diff --git a/executable_semantics/testdata/global_variable3.golden b/executable_semantics/testdata/global_variable3.golden
index bea966af02b8d..6b4a374ede660 100644
--- a/executable_semantics/testdata/global_variable3.golden
+++ b/executable_semantics/testdata/global_variable3.golden
@@ -1,4 +1,4 @@
 COMPILATION ERROR: 7: type error in initializer of variable
-expected: Int
+expected: i32
 actual: Bool
 EXIT CODE: 255
diff --git a/executable_semantics/testdata/global_variable4.carbon b/executable_semantics/testdata/global_variable4.carbon
index fcf6d61011f5a..28c5b13c8b8b5 100644
--- a/executable_semantics/testdata/global_variable4.carbon
+++ b/executable_semantics/testdata/global_variable4.carbon
@@ -4,9 +4,9 @@
 
 // Test mutation of a global variable.
 
-var zero: Int = 1;
+var zero: i32 = 1;
 
-fn main() -> Int {
+fn main() -> i32 {
   zero = 0;
   return zero;
 }
diff --git a/executable_semantics/testdata/global_variable5.carbon b/executable_semantics/testdata/global_variable5.carbon
index f4e073a3f6cbe..a528f6e93d179 100644
--- a/executable_semantics/testdata/global_variable5.carbon
+++ b/executable_semantics/testdata/global_variable5.carbon
@@ -4,12 +4,12 @@
 
 // Test overshadowing of global variable.
 
-var x: Int = 1;
+var x: i32 = 1;
 
-fn identity(x: Int) {
+fn identity(x: i32) {
   return x;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return identity(0);
 }
diff --git a/executable_semantics/testdata/global_variable5.golden b/executable_semantics/testdata/global_variable5.golden
index 2957a9e9f596d..73323db83507a 100644
--- a/executable_semantics/testdata/global_variable5.golden
+++ b/executable_semantics/testdata/global_variable5.golden
@@ -1,4 +1,4 @@
 COMPILATION ERROR: 10: type error in return
 expected: ()
-actual: Int
+actual: i32
 EXIT CODE: 255
diff --git a/executable_semantics/testdata/global_variable6.carbon b/executable_semantics/testdata/global_variable6.carbon
index e60522229937d..b21506d09b3e9 100644
--- a/executable_semantics/testdata/global_variable6.carbon
+++ b/executable_semantics/testdata/global_variable6.carbon
@@ -4,10 +4,10 @@
 
 // Test a global variable depending on another global.
 
-var x: Int = 0;
+var x: i32 = 0;
 
-var y: Int = x;
+var y: i32 = x;
 
-fn main() -> Int {
+fn main() -> i32 {
   return y;
 }
diff --git a/executable_semantics/testdata/global_variable7.carbon b/executable_semantics/testdata/global_variable7.carbon
index 4a5ee11353716..fbdc37ae3e28a 100644
--- a/executable_semantics/testdata/global_variable7.carbon
+++ b/executable_semantics/testdata/global_variable7.carbon
@@ -4,12 +4,12 @@
 
 // Test a global variable depending on a function.
 
-fn f() -> Int {
+fn f() -> i32 {
   return 0;
 }
 
-var y: Int = f();
+var y: i32 = f();
 
-fn main() -> Int {
+fn main() -> i32 {
   return y;
 }
diff --git a/executable_semantics/testdata/global_variable8.carbon b/executable_semantics/testdata/global_variable8.carbon
index 81587984e8666..7b5379ce43552 100644
--- a/executable_semantics/testdata/global_variable8.carbon
+++ b/executable_semantics/testdata/global_variable8.carbon
@@ -5,10 +5,10 @@
 // Test that a global variable may not depend on a later global.
 // Error expected.
 
-var x: Int = y;
+var x: i32 = y;
 
-var y: Int = 0;
+var y: i32 = 0;
 
-fn main() -> Int {
+fn main() -> i32 {
   return x;
 }
diff --git a/executable_semantics/testdata/if_else.carbon b/executable_semantics/testdata/if_else.carbon
index 86751e380d75d..8b0402c005a02 100644
--- a/executable_semantics/testdata/if_else.carbon
+++ b/executable_semantics/testdata/if_else.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   if (0 == 1) {
     return 1;
   } else {
diff --git a/executable_semantics/testdata/if_else_if.carbon b/executable_semantics/testdata/if_else_if.carbon
index f7b76917d3568..e6d65b491a5eb 100644
--- a/executable_semantics/testdata/if_else_if.carbon
+++ b/executable_semantics/testdata/if_else_if.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   if (0 == 1) {
     return 1;
   } else if (0 == 0) {
diff --git a/executable_semantics/testdata/if_else_if_else.carbon b/executable_semantics/testdata/if_else_if_else.carbon
index 7de528cad7958..63d61ca03ae80 100644
--- a/executable_semantics/testdata/if_else_if_else.carbon
+++ b/executable_semantics/testdata/if_else_if_else.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   if (0 == 1) {
     return 1;
   } else if (0 == 2) {
diff --git a/executable_semantics/testdata/if_false.carbon b/executable_semantics/testdata/if_false.carbon
index d1f4796ebcbf7..a457ef53a5d0b 100644
--- a/executable_semantics/testdata/if_false.carbon
+++ b/executable_semantics/testdata/if_false.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   if (0 == 1) {
     return 1;
   }
diff --git a/executable_semantics/testdata/if_nesting.carbon b/executable_semantics/testdata/if_nesting.carbon
index 50afee2c554ba..e20a13292e925 100644
--- a/executable_semantics/testdata/if_nesting.carbon
+++ b/executable_semantics/testdata/if_nesting.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   if (0 == 0) {
     if (0 == 1) {
       return 1;
diff --git a/executable_semantics/testdata/if_true.carbon b/executable_semantics/testdata/if_true.carbon
index 5503e624eb954..eb068817b1455 100644
--- a/executable_semantics/testdata/if_true.carbon
+++ b/executable_semantics/testdata/if_true.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   if (1 == 1) {
     return 0;
   }
diff --git a/executable_semantics/testdata/ignored_parameter.carbon b/executable_semantics/testdata/ignored_parameter.carbon
index fbe00104243c4..0c145b98ed02c 100644
--- a/executable_semantics/testdata/ignored_parameter.carbon
+++ b/executable_semantics/testdata/ignored_parameter.carbon
@@ -2,10 +2,10 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn ReturnSecond(_: Int, x: Int) -> Int {
+fn ReturnSecond(_: i32, x: i32) -> i32 {
   return x;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return ReturnSecond(1, 0);
 }
diff --git a/executable_semantics/testdata/match_any_int.carbon b/executable_semantics/testdata/match_any_int.carbon
index 2bed2e8214386..8f7393d70cc48 100644
--- a/executable_semantics/testdata/match_any_int.carbon
+++ b/executable_semantics/testdata/match_any_int.carbon
@@ -2,10 +2,10 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   var t: auto = 5;
   match (t) {
-    case x: Int =>
+    case x: i32 =>
       return x - 5;
   }
 }
diff --git a/executable_semantics/testdata/match_int.carbon b/executable_semantics/testdata/match_int.carbon
index 1a96c676b9934..f4f43cd9fb558 100644
--- a/executable_semantics/testdata/match_int.carbon
+++ b/executable_semantics/testdata/match_int.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   var t: auto = 5;
   match (t) {
     case 5 =>
diff --git a/executable_semantics/testdata/match_int_default.carbon b/executable_semantics/testdata/match_int_default.carbon
index af0a9e1bf1007..41a7b77089291 100644
--- a/executable_semantics/testdata/match_int_default.carbon
+++ b/executable_semantics/testdata/match_int_default.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   var t: auto = 5;
   match (t) {
     case 3 =>
diff --git a/executable_semantics/testdata/match_placeholder.carbon b/executable_semantics/testdata/match_placeholder.carbon
index 7b9fddc045dd1..c0d3fc787779b 100644
--- a/executable_semantics/testdata/match_placeholder.carbon
+++ b/executable_semantics/testdata/match_placeholder.carbon
@@ -2,10 +2,10 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   var t: auto = (1, 2, 3, 4);
   match (t) {
-    case (_: Int, _: auto, x: Int, y: auto) =>
+    case (_: i32, _: auto, x: i32, y: auto) =>
       return y - x - 1;
   }
 }
diff --git a/executable_semantics/testdata/next.carbon b/executable_semantics/testdata/next.carbon
index 865899e86ee08..c64099d30d4b2 100644
--- a/executable_semantics/testdata/next.carbon
+++ b/executable_semantics/testdata/next.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main () -> Int
+fn main () -> i32
 {
-  var x: Int = 0;
+  var x: i32 = 0;
   return x;
 }
diff --git a/executable_semantics/testdata/no_match.carbon b/executable_semantics/testdata/no_match.carbon
index fc9b2bc4b4314..9bb13a72650e7 100644
--- a/executable_semantics/testdata/no_match.carbon
+++ b/executable_semantics/testdata/no_match.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
-  var x: Int = 0;
+fn main() -> i32 {
+  var x: i32 = 0;
   match (x) {
     case 1 =>
       return 1;
diff --git a/executable_semantics/testdata/pattern_init.carbon b/executable_semantics/testdata/pattern_init.carbon
index c51f4e831237a..0edfae10e3299 100644
--- a/executable_semantics/testdata/pattern_init.carbon
+++ b/executable_semantics/testdata/pattern_init.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   var (x: auto, y: auto) = (2, 3);
   return y - x - 1;
 }
diff --git a/executable_semantics/testdata/pattern_variable_fail.carbon b/executable_semantics/testdata/pattern_variable_fail.carbon
index 35acad1e77de9..d4fe677c76317 100644
--- a/executable_semantics/testdata/pattern_variable_fail.carbon
+++ b/executable_semantics/testdata/pattern_variable_fail.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   // error
-  x : Int;
+  x : i32;
   return 1;
 }
diff --git a/executable_semantics/testdata/placeholder_variable.carbon b/executable_semantics/testdata/placeholder_variable.carbon
index 2fb18aded34dd..0d774ed46f381 100644
--- a/executable_semantics/testdata/placeholder_variable.carbon
+++ b/executable_semantics/testdata/placeholder_variable.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   var _: auto = 1;
   return 0;
 }
diff --git a/executable_semantics/testdata/record1.carbon b/executable_semantics/testdata/record1.carbon
index 3d505c65edafc..88acdcccdf15c 100644
--- a/executable_semantics/testdata/record1.carbon
+++ b/executable_semantics/testdata/record1.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
-  var t2: (.x = Int, .y = Int) = (.x = 2, .y = 5);
+fn main() -> i32 {
+  var t2: (.x = i32, .y = i32) = (.x = 2, .y = 5);
   t2.y = 3;
   return t2.y - t2.x - 1; // 3 - 2 - 1
 }
diff --git a/executable_semantics/testdata/return_empty_explicit.carbon b/executable_semantics/testdata/return_empty_explicit.carbon
index 0b61343418138..5bb3bc0e3787c 100644
--- a/executable_semantics/testdata/return_empty_explicit.carbon
+++ b/executable_semantics/testdata/return_empty_explicit.carbon
@@ -6,7 +6,7 @@ fn F() -> () {
   return ();
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   F();
   return 0;
 }
diff --git a/executable_semantics/testdata/return_empty_implicit1.carbon b/executable_semantics/testdata/return_empty_implicit1.carbon
index f2b772ba61c05..1a58d4649cb1f 100644
--- a/executable_semantics/testdata/return_empty_implicit1.carbon
+++ b/executable_semantics/testdata/return_empty_implicit1.carbon
@@ -5,7 +5,7 @@
 fn F() {
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   F();
   return 0;
 }
diff --git a/executable_semantics/testdata/return_empty_implicit2.carbon b/executable_semantics/testdata/return_empty_implicit2.carbon
index 433d1bbf97a28..9d83194a62f34 100644
--- a/executable_semantics/testdata/return_empty_implicit2.carbon
+++ b/executable_semantics/testdata/return_empty_implicit2.carbon
@@ -6,7 +6,7 @@ fn F() {
   return;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   F();
   return 0;
 }
diff --git a/executable_semantics/testdata/star.carbon b/executable_semantics/testdata/star.carbon
index 3d943f2a13b60..58bbb3e34c51f 100644
--- a/executable_semantics/testdata/star.carbon
+++ b/executable_semantics/testdata/star.carbon
@@ -3,14 +3,14 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 // Never actually called, so this only tests typechecking and semantic analysis.
-fn F(n: Int, p: Int*, q: Int***) -> Int* {
-  var a: Int = n * *p;
-  var b: Int = a*n;
+fn F(n: i32, p: i32*, q: i32***) -> i32* {
+  var a: i32 = n * *p;
+  var b: i32 = a*n;
   *p = b*(*p);
   **q = p;
   return **q;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return 0;
 }
diff --git a/executable_semantics/testdata/struct1.carbon b/executable_semantics/testdata/struct1.carbon
index 142707ef0d87d..0679506e1f2d7 100644
--- a/executable_semantics/testdata/struct1.carbon
+++ b/executable_semantics/testdata/struct1.carbon
@@ -3,11 +3,11 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 struct Point {
-  var x: Int;
-  var y: Int;
+  var x: i32;
+  var y: i32;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   var p: auto = Point(.x = 1, .y = 2);
   return p.y - p.x - 1;
 }
diff --git a/executable_semantics/testdata/struct2.carbon b/executable_semantics/testdata/struct2.carbon
index dd195aac82276..e4e3f71895503 100644
--- a/executable_semantics/testdata/struct2.carbon
+++ b/executable_semantics/testdata/struct2.carbon
@@ -3,11 +3,11 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 struct Point {
-  var x: Int;
-  var y: Int;
+  var x: i32;
+  var y: i32;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   var p1: auto = Point(.x = 1, .y = 2);
   var p2: auto = p1;
   p2.x = 3;
diff --git a/executable_semantics/testdata/struct3.carbon b/executable_semantics/testdata/struct3.carbon
index ec6f819ac0745..967ea3dee543d 100644
--- a/executable_semantics/testdata/struct3.carbon
+++ b/executable_semantics/testdata/struct3.carbon
@@ -3,10 +3,10 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 struct Point {
-  var x: Int;
-  var y: Int;
+  var x: i32;
+  var y: i32;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return Point(.x = 1, .y = 2).x - 1;
 }
diff --git a/executable_semantics/testdata/struct_field_access_mismatch.carbon b/executable_semantics/testdata/struct_field_access_mismatch.carbon
index c4c0ecc62358d..62f1949cc6d67 100644
--- a/executable_semantics/testdata/struct_field_access_mismatch.carbon
+++ b/executable_semantics/testdata/struct_field_access_mismatch.carbon
@@ -3,10 +3,10 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 struct Point {
-  var x: Int;
-  var y: Int;
+  var x: i32;
+  var y: i32;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return Point(.x = 1, .y = 2).z - 1;
 }
diff --git a/executable_semantics/testdata/struct_field_mismatch.carbon b/executable_semantics/testdata/struct_field_mismatch.carbon
index 57170f0437eb1..76900787ab3ec 100644
--- a/executable_semantics/testdata/struct_field_mismatch.carbon
+++ b/executable_semantics/testdata/struct_field_mismatch.carbon
@@ -3,10 +3,10 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 struct Point {
-  var x: Int;
-  var y: Int;
+  var x: i32;
+  var y: i32;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return Point(.x = 1, .z = 2).x - 1;
 }
diff --git a/executable_semantics/testdata/struct_field_mismatch.golden b/executable_semantics/testdata/struct_field_mismatch.golden
index a4463ac38bad0..6f8e2d2ffd7b8 100644
--- a/executable_semantics/testdata/struct_field_mismatch.golden
+++ b/executable_semantics/testdata/struct_field_mismatch.golden
@@ -1,4 +1,4 @@
 COMPILATION ERROR: 11: type error in call
-expected: (x = Int, y = Int)
-actual: (x = Int, z = Int)
+expected: (x = i32, y = i32)
+actual: (x = i32, z = i32)
 EXIT CODE: 255
diff --git a/executable_semantics/testdata/struct_field_missing.carbon b/executable_semantics/testdata/struct_field_missing.carbon
index 9912bcfd9cd5f..66c13f3e8d297 100644
--- a/executable_semantics/testdata/struct_field_missing.carbon
+++ b/executable_semantics/testdata/struct_field_missing.carbon
@@ -3,10 +3,10 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 struct Point {
-  var x: Int;
-  var y: Int;
+  var x: i32;
+  var y: i32;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return Point(.x = 1).x - 1;
 }
diff --git a/executable_semantics/testdata/struct_field_missing.golden b/executable_semantics/testdata/struct_field_missing.golden
index 9c4a56440c097..1131c81865950 100644
--- a/executable_semantics/testdata/struct_field_missing.golden
+++ b/executable_semantics/testdata/struct_field_missing.golden
@@ -1,4 +1,4 @@
 COMPILATION ERROR: 11: type error in call
-expected: (x = Int, y = Int)
-actual: (x = Int)
+expected: (x = i32, y = i32)
+actual: (x = i32)
 EXIT CODE: 255
diff --git a/executable_semantics/testdata/tuple1.carbon b/executable_semantics/testdata/tuple1.carbon
index a3912a14b8d31..455ee40864a4b 100644
--- a/executable_semantics/testdata/tuple1.carbon
+++ b/executable_semantics/testdata/tuple1.carbon
@@ -2,9 +2,9 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
-  var x: Int = (1);
-  var t2: (Int,Int) = (5, 2);
+fn main() -> i32 {
+  var x: i32 = (1);
+  var t2: (i32,i32) = (5, 2);
   t2[0] = 3;
   return t2[0] - t2[1] - x;
 }
diff --git a/executable_semantics/testdata/tuple2.carbon b/executable_semantics/testdata/tuple2.carbon
index d906888a04f54..ebaaffd8e00ce 100644
--- a/executable_semantics/testdata/tuple2.carbon
+++ b/executable_semantics/testdata/tuple2.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
-  var t1: (Int,) = (5,);
-  var t2: (Int, Int) = (2, 3,);
+fn main() -> i32 {
+  var t1: (i32,) = (5,);
+  var t2: (i32, i32) = (2, 3,);
   return t1[0] - t2[0] - t2[1];
 }
diff --git a/executable_semantics/testdata/tuple3.carbon b/executable_semantics/testdata/tuple3.carbon
index e43ac4e0600ff..9fb60c2b47ebd 100644
--- a/executable_semantics/testdata/tuple3.carbon
+++ b/executable_semantics/testdata/tuple3.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
-  var t: (Int, .x = Int) = (3, .x = 2);
+fn main() -> i32 {
+  var t: (i32, .x = i32) = (3, .x = 2);
   return t.x + 1 - t[0];
 }
diff --git a/executable_semantics/testdata/tuple4.carbon b/executable_semantics/testdata/tuple4.carbon
index f02dbc81a6e46..956483aacb37b 100644
--- a/executable_semantics/testdata/tuple4.carbon
+++ b/executable_semantics/testdata/tuple4.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   var t: auto = (.x = 2, 3);
   return 0;
 }
diff --git a/executable_semantics/testdata/tuple5.carbon b/executable_semantics/testdata/tuple5.carbon
index b89be69549372..d40779c29f90a 100644
--- a/executable_semantics/testdata/tuple5.carbon
+++ b/executable_semantics/testdata/tuple5.carbon
@@ -4,7 +4,7 @@
 
 // Test the that field order matters for tuples.
 
-fn main() -> Int {
-  var t: (.x = Int, .y = Int) = (.y = 2, .x = 3);
+fn main() -> i32 {
+  var t: (.x = i32, .y = i32) = (.y = 2, .x = 3);
   return 0;
 }
diff --git a/executable_semantics/testdata/tuple5.golden b/executable_semantics/testdata/tuple5.golden
index 56845af412d4c..eccc17107b43c 100644
--- a/executable_semantics/testdata/tuple5.golden
+++ b/executable_semantics/testdata/tuple5.golden
@@ -1,4 +1,4 @@
 COMPILATION ERROR: 8: type error in pattern variable
-expected: (x = Int, y = Int)
-actual: (y = Int, x = Int)
+expected: (x = i32, y = i32)
+actual: (y = i32, x = i32)
 EXIT CODE: 255
diff --git a/executable_semantics/testdata/tuple_assign.carbon b/executable_semantics/testdata/tuple_assign.carbon
index 94f5f6f2d7d2a..f8717764c7a05 100644
--- a/executable_semantics/testdata/tuple_assign.carbon
+++ b/executable_semantics/testdata/tuple_assign.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   var x: auto = 0;
   var y: auto = 1;
   (x, y) = (5, -5);
diff --git a/executable_semantics/testdata/tuple_equality.carbon b/executable_semantics/testdata/tuple_equality.carbon
index de3bbe321bf84..fcc1cf21f083d 100644
--- a/executable_semantics/testdata/tuple_equality.carbon
+++ b/executable_semantics/testdata/tuple_equality.carbon
@@ -2,9 +2,9 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
-  var t1: (Int,Int) = (5, 2);
-  var t2: (Int,Int) = (5, 2);
+fn main() -> i32 {
+  var t1: (i32,i32) = (5, 2);
+  var t2: (i32,i32) = (5, 2);
   if (t1 == t2) {
     return 0;
   } else {
diff --git a/executable_semantics/testdata/tuple_equality2.carbon b/executable_semantics/testdata/tuple_equality2.carbon
index 90649bfa88e87..507ebe1a14463 100644
--- a/executable_semantics/testdata/tuple_equality2.carbon
+++ b/executable_semantics/testdata/tuple_equality2.carbon
@@ -2,9 +2,9 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
-  var t1: (Int,Int) = (5, 2);
-  var t2: (Int,Int) = (5, 4);
+fn main() -> i32 {
+  var t1: (i32,i32) = (5, 2);
+  var t2: (i32,i32) = (5, 4);
   if (t1 == t2) {
     return 1;
   } else {
diff --git a/executable_semantics/testdata/tuple_equality3.carbon b/executable_semantics/testdata/tuple_equality3.carbon
index d5b71a4233c9f..00a694a1c5f5b 100644
--- a/executable_semantics/testdata/tuple_equality3.carbon
+++ b/executable_semantics/testdata/tuple_equality3.carbon
@@ -2,9 +2,9 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
-  var t1: (Int,Int) = (5, 2);
-  var t2: (Int,) = (5,);
+fn main() -> i32 {
+  var t1: (i32,i32) = (5, 2);
+  var t2: (i32,) = (5,);
   if (t1 == t2) {
     return 1;
   } else {
diff --git a/executable_semantics/testdata/tuple_equality3.golden b/executable_semantics/testdata/tuple_equality3.golden
index 6cdc4b8eb2231..ff31cb848557a 100644
--- a/executable_semantics/testdata/tuple_equality3.golden
+++ b/executable_semantics/testdata/tuple_equality3.golden
@@ -1,4 +1,4 @@
 COMPILATION ERROR: 8: type error in ==
-expected: (0 = Int, 1 = Int)
-actual: (0 = Int)
+expected: (0 = i32, 1 = i32)
+actual: (0 = i32)
 EXIT CODE: 255
diff --git a/executable_semantics/testdata/tuple_match.carbon b/executable_semantics/testdata/tuple_match.carbon
index b8073fc102cd0..9a54232ad7b0f 100644
--- a/executable_semantics/testdata/tuple_match.carbon
+++ b/executable_semantics/testdata/tuple_match.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   var t: auto = (5, 2);
   match (t) {
     case (a: auto, b: auto) =>
diff --git a/executable_semantics/testdata/tuple_match2.carbon b/executable_semantics/testdata/tuple_match2.carbon
index 53c6dbc3e218a..2f79de431b6c0 100644
--- a/executable_semantics/testdata/tuple_match2.carbon
+++ b/executable_semantics/testdata/tuple_match2.carbon
@@ -4,7 +4,7 @@
 
 // Test matching with a mixture of positional and named fields.
 
-fn main() -> Int {
+fn main() -> i32 {
   var t: auto = (2, .x = 5);
   match (t) {
     case (a: auto, .x = b: auto) =>
diff --git a/executable_semantics/testdata/tuple_match3.carbon b/executable_semantics/testdata/tuple_match3.carbon
index e0572188f8b06..f65310fd5388d 100644
--- a/executable_semantics/testdata/tuple_match3.carbon
+++ b/executable_semantics/testdata/tuple_match3.carbon
@@ -4,7 +4,7 @@
 
 // Test matching of a tuple inside a tuple.
 
-fn main() -> Int {
+fn main() -> i32 {
   var t: auto = ((1,2),(3,4));
   match (t) {
     case ((a: auto, b: auto), c: auto) =>
diff --git a/executable_semantics/testdata/type_compute.carbon b/executable_semantics/testdata/type_compute.carbon
index 67a57298b5127..b7df36f7e1708 100644
--- a/executable_semantics/testdata/type_compute.carbon
+++ b/executable_semantics/testdata/type_compute.carbon
@@ -6,7 +6,7 @@ fn Id(t: Type) => t;
 
 // Test non-trivial type expression in variable declaration statement.
 
-fn main() -> Int {
-  var x: Id(Int) = 0;
+fn main() -> i32 {
+  var x: Id(i32) = 0;
   return x;
 }
diff --git a/executable_semantics/testdata/type_compute2.carbon b/executable_semantics/testdata/type_compute2.carbon
index 5898154b4bdfa..7f7322b03f93d 100644
--- a/executable_semantics/testdata/type_compute2.carbon
+++ b/executable_semantics/testdata/type_compute2.carbon
@@ -6,6 +6,6 @@ fn Id(t: Type) => t;
 
 // Test non-trivial type expression in return type.
 
-fn main() -> Id(Int) {
+fn main() -> Id(i32) {
   return 0;
 }
diff --git a/executable_semantics/testdata/type_compute3.carbon b/executable_semantics/testdata/type_compute3.carbon
index 7b6fdf50cd8dd..424a8dd7258ea 100644
--- a/executable_semantics/testdata/type_compute3.carbon
+++ b/executable_semantics/testdata/type_compute3.carbon
@@ -6,10 +6,10 @@ fn Id(t: Type) => t;
 
 // Test non-trivial type expression in parameter type.
 
-fn f(x: Id(Int)) -> Int {
+fn f(x: Id(i32)) -> i32 {
   return x;
 }
 
-fn main() -> Int {
+fn main() -> i32 {
   return f(0);
 }
diff --git a/executable_semantics/testdata/while1.carbon b/executable_semantics/testdata/while1.carbon
index 772246167df10..5215e4000fa1d 100644
--- a/executable_semantics/testdata/while1.carbon
+++ b/executable_semantics/testdata/while1.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   var x: auto = 2;
   while (not (x == 0)) {
     x = x - 1;
diff --git a/executable_semantics/testdata/zero.carbon b/executable_semantics/testdata/zero.carbon
index 85911ed193e60..7a87538724c86 100644
--- a/executable_semantics/testdata/zero.carbon
+++ b/executable_semantics/testdata/zero.carbon
@@ -2,6 +2,6 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-fn main() -> Int {
+fn main() -> i32 {
   return 0;
 }