diff --git a/docs/rules/0134/response-lro.md b/docs/rules/0134/response-lro.md
new file mode 100644
index 000000000..46f1ab7d6
--- /dev/null
+++ b/docs/rules/0134/response-lro.md
@@ -0,0 +1,79 @@
+---
+rule:
+  aip: 134
+  name: [core, '0134', response-lro]
+  summary: |
+    Declarative-friendly Update methods should use long-running operations.
+permalink: /134/response-lro
+redirect_from:
+  - /0134/response-lro
+---
+
+# Long-running Update
+
+This rule enforces that declarative-friendly update methods use long-running
+operations, as mandated in [AIP-134][].
+
+## Details
+
+This rule looks at any `Update` method connected to a resource with a
+`google.api.resource` annotation that includes `style: DECLARATIVE_FRIENDLY`,
+and complains if it does not use long-running operations.
+
+## Examples
+
+**Incorrect** code for this rule:
+
+```proto
+// Incorrect.
+// Assuming that Book is styled declarative-friendly, UpdateBook should
+// return a long-running operation.
+rpc UpdateBook(UpdateBookRequest) returns (Book) {
+  option (google.api.http) = {
+    patch: "/v1/{book.name=publishers/*/books/*}"
+    body: "book"
+  };
+}
+```
+
+**Correct** code for this rule:
+
+```proto
+// Correct.
+// Assuming that Book is styled declarative-friendly...
+rpc UpdateBook(UpdateBookRequest) returns (google.longrunning.Operation) {
+  option (google.api.http) = {
+    patch: "/v1/{book.name=publishers/*/books/*}"
+    body: "book"
+  };
+  option (google.longrunning.operation_info) = {
+    response_type: "Book"
+    metadata_type: "OperationMetadata"
+  };
+}
+```
+
+## Disabling
+
+If you need to violate this rule, use a leading comment above the message.
+Remember to also include an [aip.dev/not-precedent][] comment explaining why.
+
+```proto
+// (-- api-linter: core::0134::response-lro=disabled
+//     aip.dev/not-precedent: We need to do this because reasons. --)
+rpc UpdateBook(UpdateBookRequest) returns (Book) {
+  option (google.api.http) = {
+    patch: "/v1/{book.name=publishers/*/books/*}"
+    body: "book"
+  };
+}
+```
+
+**Note:** Violations of declarative-friendly rules should be rare, as tools are
+likely to expect strong consistency.
+
+If you need to violate this rule for an entire file, place the comment at the
+top of the file.
+
+[aip-134]: https://aip.dev/134
+[aip.dev/not-precedent]: https://aip.dev/not-precedent
diff --git a/rules/aip0134/aip0134.go b/rules/aip0134/aip0134.go
index ae123282c..ae850f554 100644
--- a/rules/aip0134/aip0134.go
+++ b/rules/aip0134/aip0134.go
@@ -40,6 +40,7 @@ func AddRules(r lint.RuleRegistry) error {
 		requestMessageName,
 		requestResourceField,
 		requestResourceRequired,
+		responseLRO,
 		synonyms,
 		unknownFields,
 	)
diff --git a/rules/aip0134/response_lro.go b/rules/aip0134/response_lro.go
new file mode 100644
index 000000000..e9b779c79
--- /dev/null
+++ b/rules/aip0134/response_lro.go
@@ -0,0 +1,40 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package aip0134
+
+import (
+	"github.com/googleapis/api-linter/lint"
+	"github.com/googleapis/api-linter/locations"
+	"github.com/googleapis/api-linter/rules/internal/utils"
+	"github.com/jhump/protoreflect/desc"
+)
+
+var responseLRO = &lint.MethodRule{
+	Name: lint.NewRuleName(134, "response-lro"),
+	OnlyIf: func(m *desc.MethodDescriptor) bool {
+		return isUpdateMethod(m) && utils.IsDeclarativeFriendlyMethod(m)
+	},
+	LintMethod: func(m *desc.MethodDescriptor) []lint.Problem {
+		if m.GetOutputType().GetFullyQualifiedName() != "google.longrunning.Operation" {
+			return []lint.Problem{{
+				Message:    "Declarative-friendly update methods should use an LRO.",
+				Descriptor: m,
+				Location:   locations.MethodResponseType(m),
+				Suggestion: "google.longrunning.Operation",
+			}}
+		}
+		return nil
+	},
+}
diff --git a/rules/aip0134/response_lro_test.go b/rules/aip0134/response_lro_test.go
new file mode 100644
index 000000000..b8e17bb3a
--- /dev/null
+++ b/rules/aip0134/response_lro_test.go
@@ -0,0 +1,60 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package aip0134
+
+import (
+	"testing"
+
+	"github.com/googleapis/api-linter/rules/internal/testutils"
+)
+
+func TestResponseLRO(t *testing.T) {
+	problems := testutils.Problems{{Suggestion: "google.longrunning.Operation"}}
+	for _, test := range []struct {
+		name         string
+		Style        string
+		ResponseType string
+		problems     testutils.Problems
+	}{
+		{"ValidNotDF", "", "Book", nil},
+		{"ValidLRO", "style: DECLARATIVE_FRIENDLY", "google.longrunning.Operation", nil},
+		{"InvalidDFSync", "style: DECLARATIVE_FRIENDLY", "Book", problems},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			f := testutils.ParseProto3Tmpl(t, `
+				import "google/api/resource.proto";
+				import "google/longrunning/operations.proto";
+
+				service Library {
+					rpc UpdateBook(UpdateBookRequest) returns ({{.ResponseType}});
+				}
+
+				message Book {
+					option (google.api.resource) = {
+						type: "library.googleapis.com/Book"
+						pattern: "publishers/{publisher}/books/{book}"
+						{{.Style}}
+					};
+				}
+
+				message UpdateBookRequest {}
+			`, test)
+			m := f.GetServices()[0].GetMethods()[0]
+			if diff := test.problems.SetDescriptor(m).Diff(responseLRO.Lint(f)); diff != "" {
+				t.Errorf(diff)
+			}
+		})
+	}
+}