This pilot study used a randomized controlled trial to test the efficacy of an HIV risk-reduction intervention for university students in Eastern Cape Province, South Africa. Randomly selected second-year students were randomized to one of two interventions based on social cognitive theory and qualitative research: HIV risk-reduction, targeting sexual-risk behaviors; health-promotion control, targeting health behaviors unrelated to sexual risks. Participants completed behavioral assessments via audio computer-assisted self-interviewing pre-intervention, 6, and 12 months post intervention, with 97.2% retained at 12-month follow-up. Averaged over the 2 follow-ups, HIV risk-reduction intervention participants reported less unprotected vaginal intercourse and more frequent condom use than control participants, with greater efficacy in non-South Africans than South Africans. Positive changes were also observed on theoretical mediators of condom use that the intervention targeted. Interventions based on social cognitive theory integrated with qualitative information from the population may reduce sexual risk behaviors among university students in sub-Saharan Africa.