The authors conducted a voluntary serosurvey and educational campaign among 3394 undergraduate students attending the University of Maryland at College Park to determine the prevalence of and risk factors for human immunodeficiency virus type 1 (HIV-1) infection. Two students were seropositive (0.06%, 95% confidence interval 0-0.15%). Both were homosexual men with multiple sexual partners. Despite the low prevalence of infection, potential risk factors for transmission of HIV-1 were common, as assessed by a self-administered anonymous questionnaire. These included a previous sexually transmitted disease (12.6%), male homosexual intercourse (4.8% of men), heterosexual anal intercourse (25.3%), heterosexual intercourse with a person at risk (an HIV-1 infected person, a bisexual man, a parenteral drug user, a female prostitute, or a hemophiliac) (5.2%), multiple sexual partners (21% reported 10 or more lifetime partners), and intravenous drug use (1.3%). Assessment of the efficacy of our program by comparing responses on pre- and post-test questionnaires showed gains in knowledge about heterosexual transmission of HIV-1 and an increase in the reported frequency of condom use 1-2 months after participating in the survey. The authors conclude that HIV-1 infections are occurring among college students but in our study group remain confined to persons with known high-risk behavior; however, practices that may support transmission are common, and programs designed to diminish these behaviors among college students are needed.