BACKGROUND. Stress among medical students has been linked to poor academic performance, while supportive social relationships have been associated with the alleviation of psychological stress. This study examines social support as a potential buffer against stress and hence as a potential strengthener of students' academic performances. METHOD. A cohort of 153 third-year students at the University of Illinois College of Medicine at Chicago was asked in the fall of 1990 to complete a questionnaire assessing role stress (stress involving competing demands between school and social and/or family life), social support, and sources of support (outside or inside medical school). Grades for the five major clerkships through which all the students rotated during their third year were collected from student transcripts. Statistical analyses of the relationships among academic performance, stress, and social support included factor analysis, hierarchical multiple-regression analysis, and Pearson correlational analysis. RESULTS. Data from 120 students (78% of the cohort) were used for correlational analysis. Of these students, 79 (66%) were men and 41 (34%) were women. Because eight of the questionnaires contained incomplete data, 112 questionnaires (73%) were used for multiple-regression analysis. No buffering effect was found for social support. Rather, social support from outside the medical school explained significant variance in academic performances and in role stress. Higher levels of outside support were associated with poorer clerkship grades for women, but with lower levels of stress for men. Also, total support (outside and inside combined) was negatively related to clerkship grades for the entire sample. CONCLUSION. The results suggest that contrary to the study's hypotheses, social support in general is related to lower levels of academic performance for both men and women, and that the negative effects of support from outside the medical school context may be particularly salient for women. These results are understandable given the nature of medical training, which places great demands on students' time. Therefore, it may be more appropriate for medical schools to promote time-management strategies than support-building interventions, especially for women.