OBJECTIVES: We estimated the prevalence of same-sex experience among women and compared women reporting sex with women and men and women reporting sex exclusively with women with women reporting sex exclusively with men, in terms of sociodemographics and sexual, reproductive, and general health risk behaviors and outcomes. METHODS: We used a British probability survey (n=6399 women, aged 16 to 44 years) conducted from 1999 to 2001 with face-to-face interviewing and computer-assisted self-interviewing. RESULTS: We found that 4.9% of the women reported same-sex partner(s) ever; 2.8% reported sex with women in the past 5 years (n=178); 85.0% of these women also reported male partner(s) in this time. Compared with women who reported sex exclusively with men, women who reported sex with women and men reported significantly greater male partner numbers, unsafe sex, smoking, alcohol consumption, and intravenous drug use and had an increased likelihood of induced abortion and sexually transmitted infection diagnoses (age-adjusted odds ratios=3.07 and 4.41, respectively). CONCLUSIONS: For women, a history of sex with women may be a marker for increased risk of adverse sexual, reproductive, and general health outcomes compared with women who reported sex exclusively with men. A nonjudgmental review of female patients' sexual history should help practitioners discuss risks that women may face.