This document compares AJAX and Flex technologies for building rich internet applications (RIAs). It provides examples of applications built with each technology. AJAX allows updating parts of a web page asynchronously using JavaScript, XML, and CSS. Flex is a framework for building RIAs using ActionScript code. Both have benefits for developers and enterprises. The document concludes that AJAX is better for small, frequent updates while Flex is better for large, complex applications requiring rich media. It also provides an example of how AJAX and Flex can be used together interoperably in a single application.