DrillKit is a new type of modular and extensible e-learning application. It is built on top of the Content Management System (CMS) called Drupal. DrillKit's structure and interaction design is based on current educational research and usability test data.DrillKit's main goal is to provide an easy-to-use interface for presenting and learning material online. Initially, it will be used to teach medical students about Substance Abuse and Dependence. Other areas will be added later. Thus, in addition to the Concepts, Quizzes, and Glossary tools, it features a Clinical Case tool. Concepts are presented in a hierarchical manner with an emphasis on learning objectives and main points. Users can "drill down" from area, topic, lesson, objective, to specific points. Each point can have optional supplementary resources attached to it. Material can also be cross-referenced using the Related Resources feature. Educational research has shown that student interaction via testing improves learning, and in Drillkit, learning is facilitated when students learn from testing and repetition (“drill”) by working through clinical cases and answering questions or taking quizzes related to each teaching point. Students receive immediate feedback to their answers and also cross-reference to the original material and related resources. The National Institute on Drug Abuse supported the construction of Drillkit by George R. Heninger MD,professor of Psychiatry, Yale Medical School and Mai Irie, computer programmer analyst.