Recently, the extraordinary growth in the World Wide Web has been sweeping through business and industry. Many companies have developed or integrated their mission-critical applications using Web technologies. As Web applications become complex, testing Web applications becomes crucial. This paper extends traditional data flow-testing techniques to Web applications. Several data flow issues for analyzing HTML documents in Web applications are discussed. A test model that captures data flow test artifacts of Web applications is presented. In the test model, each component of a Web application is modeled as an object. The data flow information of the Web application is captured using flow graphs. From the test model, data flow test cases for the Web application then can be derived based on the intra-object, and inter-client perspectives.