This study examined the differential patterns of alcohol outcome expectancies in relation to drinking before sex and having sex partners who drink before sex among men (N=614) and women (N=158) sexually transmitted infections clinic patients in Cape Town South Africa. Hierarchical regressions, controlling for age, education, and alcohol use showed that men's sexual enhancement alcohol expectancies were associated with drinking before sex and having sex partners who drank before sex. Behavioral disinhibition expectancies were inversely related to drinking before sex. For women, there were no associations between alcohol expectancies and drinking before sex, although sexual enhancement expectancies were related to having sex partners who drank before sex. We conclude that alcohol outcome expectancies, particularly expectancies that alcohol will enhance sexual experiences, are related to HIV transmission risks. Sexual risk reduction interventions for those at greatest risk for HIV/AIDS should directly address alcohol expectancies.