This paper presents the design of a project-based study environment on the World Wide Web based upon the e-study concept, i.e., studying by means of Internet technologies. The first section discusses the e-study concept, including Interactive Study Environments (ISE), Interactive Study Systems, and online Study Services. Design guidelines for a project-based study environment on the Web are presented in the second section, including three phases (prepare, guide, and evaluate education). The following generic guidelines related to all three phases are summarized: users need to be able to up- and download information; users have to be able to communicate with each other; users need appropriate performance support; and the instructor needs to be able to perform administrative tasks. Phase-specific guidelines are also addressed. ComMedia, an example of a project-based ISE developed at Twente University (Netherlands), is described in the third section. Two figures illustrate the e-study concept and the "Cabinet" (the online knowledge base) in ComMedia. (DLS)