The effect of a 6-week summer prematriculation program on the cognitive performance of educationally disadvantaged minority students in their first year of medical school was studied. A second objective was to determine if participation in the program strengthened the sources of social support available to minority students within the medical school. The two components of the summer program at the University of Illinois College of Medicine are self-assessment workshops (e.g., study habits and test-taking skills) and an introduction to the first year's curriculum. Disadvantaged, minority participants and nonparticipants from the classes of 1984, 1985, and 1986 were compared on their performance on the anatomy, biochemistry, and physiology components of the basic science examination given at the end of the first quarter of medical school. Multivariate analysis of variance indicated that participants scored significantly higher than did nonparticipants. Results of a questionnaire designed to evaluate social support were inconclusive. It is noted that other factors affecting students' performance include motivational reasons for participating in the program, and whether the participants applied the study and test-taking skills they acquired during the summer. (SW)