This study investigates the prevalence of self-reported experiences of discrimination based on sexual orientation among black and white women and men (25 to 37 years old) who are members of CARDIA, a multisite longitudinal study of cardiovascular risk factors. Among the 1,724 participants who responded to a 1989 questionnaire obtaining data on lifetime number of sexual partners and who participated in the Year 7 exam (1992-1993), which included questions about discrimination, 204 (12 percent) reported having at least one same-sex sexual partner: 27 (7 percent) of the 412 black women, 13 (6 percent) of the 221 black men, 87 (14 percent) of the 619 white women, and 77 (16 percent) of the 472 white men. Among these four groups, 33, 39, 52, and 56 percent, respectively, reported having experience discrimination based on sexual orientation. Additionally, 85 percent of black women and 77 percent of the black men reported having experienced racial discrimination, and 89 percent of the black women and 88 percent of the white women reported having experience gender discrimination. In the light of research associating negative stressors with poor health outcomes, including elevated blood pressure, future studies should assess public health implications of discrimination based on sexual orientation, in conjunction with racial and gender discrimination.