diff --git a/README.md b/README.md
index c954fe0..d8c3331 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,8 @@ llm keys set claude
 # Paste key here
 ```
 
+You can also set the key in the environment variable `ANTHROPIC_API_KEY`
+
 Run `llm models` to list the models, and `llm models --options` to include a list of their options.
 
 Run prompts like this: