Index: src/ajax.js
===================================================================
--- src/ajax.js	(revision 3533)
+++ src/ajax.js	(working copy)
@@ -78,6 +78,7 @@
 Ajax.Request.prototype = Object.extend(new Ajax.Base(), {
   initialize: function(url, options) {
     this.transport = Ajax.getTransport();
+    this.aborted = false;
     this.setOptions(options);
     this.request(url);
   },
@@ -103,6 +104,10 @@
 
       this.setRequestHeaders();
 
+      if (this.options.requestTimeout)
+        this.requestTimer = setTimeout((function() {this.abortRequest()}).bind(this),
+          this.options.requestTimeout * 1000);
+
       var body = this.options.postBody ? this.options.postBody : parameters;
       this.transport.send(this.options.method == 'post' ? body : null);
 
@@ -111,6 +116,11 @@
     }
   },
 
+  abortRequest: function() {
+    this.aborted = true;
+    this.transport.abort();
+  },
+
   setRequestHeaders: function() {
     var requestHeaders = 
       ['X-Requested-With', 'XMLHttpRequest',
@@ -166,25 +176,33 @@
     var transport = this.transport, json = this.evalJSON();
 
     if (event == 'Complete') {
+      if (this.requestTimer)
+        clearTimeout(this.requestTimer);
+
       try {
-        (this.options['on' + this.transport.status]
-         || this.options['on' + (this.responseIsSuccess() ? 'Success' : 'Failure')]
-         || Prototype.emptyFunction)(transport, json);
+        if (!this.aborted) {
+          (this.options['on' + this.transport.status]
+           || this.options['on' + (this.responseIsSuccess() ? 'Success' : 'Failure')]
+           || Prototype.emptyFunction)(transport, json);
+        } else {
+          (this.options['onTimeout']
+           || Prototype.emptyFunction)(transport, json);
+        }
       } catch (e) {
         this.dispatchException(e);
       }
-      
+
       if ((this.header('Content-type') || '').match(/^text\/javascript/i))
         this.evalResponse();
     }
-    
+
     try {
       (this.options['on' + event] || Prototype.emptyFunction)(transport, json);
       Ajax.Responders.dispatch('on' + event, this, transport, json);
     } catch (e) {
       this.dispatchException(e);
     }
-    
+
     /* Avoid memory leak in MSIE: clean up the oncomplete event handler */
     if (event == 'Complete')
       this.transport.onreadystatechange = Prototype.emptyFunction;
Index: CHANGELOG
===================================================================
--- CHANGELOG	(revision 3533)
+++ CHANGELOG	(working copy)
@@ -1,5 +1,7 @@
 *SVN*
 
+* Add requestTimeout option to Ajax.Request [Todd Ross]
+
 * Fix Enumerable.zip iterator behavior. [Marcin Kaszynski, sam]
 
 *1.5.0_pre0* (January 18, 2006)