We examined the efficacy and mediation of Being Responsible for Ourselves (BRO), an HIV/STI risk reduction intervention for African American men who have sex with men (MSM), the population with the highest HIV diagnosis rate in the US. We randomized African American MSM to one of two interventions: BRO HIV/STI risk reduction, targeting condom use; or attention-matched control, targeting physical activity and healthy diet. The interventions were based on social cognitive theory, the reasoned-action approach, and qualitative research. Men reporting anal intercourse with other men in the past 90 days were eligible and completed pre-intervention,