The role lectures play in problem-based learning was studied. The hypothesis was that lecture quality would have a positive influence on the time students would spend in study, that it would increase intrinsic interest in subject matter and would have a positive influence on achievement. Lecture quality would add to the other factors that play a role in problem-based learning, such as prior knowledge, the quality of the problems, the functioning of the tutor, and small-group collaboration. To test these hypotheses, data from 1,500 undergraduate students were analyzed. It was concluded that lecture quality did not affect the time spent in study, does not add to achievement, and does not influence intrinsic interest in the subject mater. Post-hoc analyses, however, demonstrated the quality of lectures to be related to other components of problem-based learning, which were not part of the presented model, such as students' perceptions of lectures as organizers of study efforts, or lectures as a means of putting the problem into a broader perspective. (Contains 4 tables, 3 figures, and 42 references.) (Author/SLD)