Because drug-involved women are among the fastest growing groups with AIDS, sexual risk reduction intervention for them is a public health imperative. To test effectiveness of HIV/STD safer sex skills building (SSB) groups for women in community drug treatment. Randomized trial of SSB versus standard HIV/STD Education (HE); assessments at baseline, 3 and 6 months. Women recruited from 12 methadone or psychosocial treatment programs in Clinical Trials Network of National Institute on Drug Abuse. Five hundred fifteen women with >or=1 unprotected vaginal or anal sex occasion (USO) with a male partner in the past 6 months were randomized. In SSB, five 90-minute groups used problem solving and skills rehearsal to increase HIV/STD risk awareness, condom use, and partner negotiation skills. In HE, one 60-minute group covered HIV/STD disease, testing, treatment, and prevention information. Number of USOs at follow-up. A significant difference in mean USOs was obtained between SSB and HE over time (F = 67.2, P < 0.0001). At 3 months, significant decrements were observed in both conditions. At 6 months, SSB maintained the decrease and HE returned to baseline (P < 0.0377). Women in SSB had 29% fewer USOs than those in HE. Skills building interventions can produce ongoing sexual risk reduction in women in community drug treatment.