This research project studied the effects of hierarchical versus heterarchical hypermedia structures of Web-based case representations on complex problem-solving skills and knowledge assembly in problem-centered learning environments in order to develop a system or model that informs the design of Web-based cases for ill-structured problems across multiple disciplines. Two groups of college students (n=3 and n=3) were assigned to work through an ill-structured problem, represented hierarchically and heterarchically in a Web-based format. A Web-based tracking program was deployed to track students journeys through the hypermedia case designs. Students were observed while interacting with the problem and were interviewed after submitting their case solutions. Results from the tracking program, observations, case solutions, and interview questions address case design issues, problem-solving issues, and group processes. Findings reveal that heterarchical case designs potentially increase student collaboration in a Web-based hypermedia design of an ill-structured problem and engage students in thinking critically about case content. (Contains 3 tables, 2 figures, and 34 references.) (Author/SLD)