In the last years, appropriate user interaction design patterns for Web Applications have been defined to improve the development and quality of such applications. Identifying which interaction design patterns are implemented in the Web client pages of an existing application may make easier some maintenance tasks, such as the re-engineering of the user interfaces. In this paper a method to support the automatic identification of interaction design patterns implemented in a Web client page is proposed. The method is based on reverse engineering techniques aiming to search the page code for those features characterizing a pattern.