The study reported in this paper has explored the use of an electronic forum facility in order to provide support for problem-based learning (PBL). A Web-based course involving the use of PBL (called "Drug and Nutrient Interactions") was implemented and was augmented with interdisciplinary expert support using electronic forums. As part of their PBL experiences, students interacted with their peers, the teacher, the facilitator and experts (a dietician, a doctor, and a librarian) in order to enhance their knowledge and complete a group project. Students' online interactions and their written reflections were used to identify the types of online support which contributed to self-directed, Web-based learning in a PBL context. The study concluded that both "cognitive support" (guidance, clarification, suggestion, inquiry, information) and "affective support" (comment, confirmation, reminding and encouragement) are needed in order to facilitate the process of learning. Overall, students were positive about this approach. (Contains 1 figure and 7 tables.)