ABSTRACT: We examined whether a cumulative genetic score (CGS) containing MAOA and 5-HTTLPR polymorphisms moderated drinking and intimate partner violence (IPV) treatment outcomes in hazardous drinking men receiving batterer intervention or batterer intervention plus a brief alcohol intervention.We conducted a randomized controlled trial with 97 hazardous drinking men who had a relationship partner and were in batterer intervention programs. Participants were randomized to receive 40 hr of standard batterer program (SBP) or the SBP plus a 90-min alcohol intervention (SBP + BAI). Data were collected at baseline, 3-, 6-, and 12-month follow-up, with follow-up rates of 99.0%, 97.9%, and 93.8%, respectively. Genomic DNA was extracted from saliva. Substance use was measured with the timeline followback interview; IPV was assessed with the Revised Conflict Tactics scales. The primary outcomes were drinks per drinking day (DDD), percentage of days abstinent from alcohol (PDA), frequency of physical IPV, and injuries to partners.Consistent with hypotheses, analyses demonstrated significant treatment condition by CGS interactions for PDA, physical violence, and injuries, but not for DDD. At high levels of the CGS, men in SBP + BAI had greater PDA (B = .16, 95% CI [.04, .27], p = .01), less physical violence perpetration (B = -1.21, 95% CI [-2.21, -.21], p = .02), and fewer injuries to partners (B = -2.37, 95% CI [-3.19, -.82], p = .00) than men in SBP. No differences between the groups in PDA, physical violence, or injuries were observed at low levels of the CGS.Findings demonstrate the potential importance of MAOA and 5-HTTLPR polymorphisms in the treatment of IPV and drinking in men in batterer intervention programs. (PsycINFO Database Record