Medical students may have negative attitudes about persons with the acquired immunodeficiency syndrome (AIDS) as well as concerns about occupational infection with human immunodeficiency virus. We conducted a brief intervention to assess and modify attitudes of first-year students. The intervention was presented to small groups of students by peers, faculty, and a person with AIDS. Assessments of attitudes and knowledge were conducted one week prior to the intervention (pretest), and one (posttest 1) and 47 weeks (posttest 2) afterwards. Females had more positive attitudes about AIDS on pretest and posttest 1. Attitude scores improved significantly from pretest to posttest 1 but returned close to baseline by posttest 2. Knowledge scores were high on pretest and did not change significantly. Attitude scores were significantly correlated with knowledge, and with students' opinions regarding obligation to care for AIDS patients. Acquaintance with a homosexual was highly correlated with both scores. This intervention may serve as a model in improving students' attitudes about AIDS.