Perceived discrimination may contribute to somatic disease. The association between perceived discrimination and breast cancer incidence was assessed in the Black Women's Health Study. In 1997, participants completed questions on perceived discrimination in two domains: "everyday" discrimination (e.g., being treated as dishonest) and major experiences of unfair treatment due to race (job, housing, and police). Cox proportional hazards models were used to estimate incidence rate ratios, controlling for breast cancer risk factors. From 1997 to 2003, 593 incident cases of breast cancer were ascertained. In the total sample, there were weak positive associations between cancer incidence and everyday and major discrimination. These associations were stronger among the younger women. Among women aged less than 50 years, those who reported frequent everyday discrimination were at higher risk than were women who reported infrequent experiences. In addition, the incidence rate ratio was 1.32 (95% confidence interval: 1.03, 1.70) for those who reported discrimination on the job and 1.48 (95% confidence interval: 1.01, 2.16) for those who reported discrimination in all three situations - housing, job, and police - relative to those who reported none. These findings suggest that perceived experiences of racism are associated with increased incidence of breast cancer among US Black women, particularly younger women.