The effectiveness of a motivational and skills training HIV/AIDS group intervention designed for men in substance abuse treatment was evaluated. Men in methadone maintenance (n = 288) or outpatient psychosocial treatment (n = 302) completed assessments at baseline, 2 weeks, 3 months, and 6 months postintervention. Participants were randomly assigned to attend either Real Men Are Safe (REMAS; five sessions containing information, motivational exercises, and skills training) or HIV education (HIV-Ed; one session containing HIV prevention information). REMAS participants engaged in significantly fewer unprotected vaginal and anal sexual intercourse occasions (USO) during the 90 days prior to the 3- and 6-month follow-ups than HIV-Ed participants. Completing REMAS resulted in an even stronger effect: Completers reduced their number of USO by 21% from baseline to 6-month follow-up. In contrast, HIV-Ed completers increased the number of USO by 2%. A motivational and skills training HIV prevention intervention designed for men was associated with greater sexual risk reduction over standard HIV-Ed. Substance abuse treatment programs can therefore help reduce sexual risk among their clientele by providing a more intensive intervention than what is traditionally provided.