This study tested the hypothesis that greater alcohol involvement will predict number of sexual partners to a greater extent for women than for men, and that the hypothesized sex-specific, alcohol—sexual partner associations will hold when controlling for alternative sex-linked explanations (i.e., depression and drug use). We recruited 508 patients (46% female, 67% African American) from a public STI clinic. Participants reported number of sexual partners, drinks per week, maximum drinks per day, frequency of heavy drinking; they also completed the AUDIT-C and a measure of alcohol problems. As expected, men reported more drinking and sexual partners. Also as expected, the association between alcohol use and number of partners was significant for women but not for men, and these associations were not explained by drug use or depression. A comprehensive prevention strategy for women attending STI clinics might include alcohol use reduction.