OBJECTIVE: We evaluated the efficacy of a brief, clinic-based, safer sex program administered by a lay health adviser for young heterosexual African American men newly diagnosed with a sexually transmitted disease (STD). METHODS: Subsequent to STD diagnosis, eligible men (N = 266; aged 18-29 years) were randomized to either a personalized, single-session intervention (delivered by a lay health adviser) or standard of care. We conducted behavioral assessments at baseline and 3 months postintervention (retention was 74.1%). We also conducted a 6-month clinic record review. RESULTS: Compared to men randomized to the control condition, those receiving the intervention were significantly less likely to acquire subsequent STDs (50.4% vs 31.9%; P = .002) and more likely to report using condoms during last sexual intercourse (72.4% vs 53.9%; P = .008). They also reported fewer sexual partners (mean 2.06 vs 4.15; P < .001) and fewer acts of unprotected sex (mean 12.3 vs 29.4; P = .045). Based on a 9-point rating scale, men in the intervention group had higher proficiency scores for condom application skills (mean difference = 3.17; P < .001). CONCLUSION: A brief clinic-based intervention delivered by a lay health adviser may be an efficacious strategy to reduce incident STDs among young heterosexual African American men.