This study assessed the short- and long-term effect of a gender-specific group intervention for women on unsafe sexual encounters and strategies for protection against HIV/STD infection. Family planning clients (N = 360) from a high HIV seroprevalence area in New York City were randomized to an eight-session, a four-session or a control condition and followed at one, six and 12 months post-intervention. Using an intention-to-treat analysis, women who were assigned to the eight-session group had about twice the odds of reporting decreased or no unprotected vaginal and anal intercourse compared to controls at one month (OR = 1.93, 95% confidence interval [CI] = 1.07, 3.48, p = 0.03) and at 12-month follow-up (OR = 1.65, 95% CI = 0.94, 2.90, p = 0.08). Relative to controls, women assigned to the eight-session condition reported during the previous month approximately three-and-a-half (p = 0.09) and five (p < 0.01) fewer unprotected sex occasions at one- and 12-month follow-up, respectively. Women in the eight-session group also reduced the number of sex occasions at both follow-ups, and had a greater odds of first time use of an alternative protective strategy (refusal, outercourse, mutual testing) at one-month follow-up. Results for the four-session group were in the expected direction but overall were inconclusive. Thus, gender-specific interventions of sufficient intensity can promote short- and long-term sexual risk reduction among women in a family planning setting.