diff --git a/README.rdoc b/README.rdoc
index 50448f18..0bf9f310 100644
--- a/README.rdoc
+++ b/README.rdoc
@@ -98,6 +98,12 @@ Or with a block parameter:
     "Hello, #{c}!"
   end
 
+Route patterns may have optional parameters:
+
+  get '/posts.?:format?' do
+    # matches "GET /posts" and any extension "GET /posts.json", "GET /posts.xml" etc.
+  end
+
 === Conditions
 
 Routes may include a variety of matching conditions, such as the user agent: