Black breast cancer patients have shorter survival compared to whites. Lack of optimal treatment may be a potential explanation for this difference. Although racial disparities in surgical and radiation therapy have been studied extensively, there is little information on racial disparities in use of adjuvant systemic therapy. Medicaid enrolled patients provide an opportunity to examine racial disparity in breast cancer treatment by minimizing the roles of access to health care and socioeconomic status. This study, therefore, compared breast cancer treatment, particularly adjuvant systemic therapy and survival in black and white women enrolled in Medicaid. Linked New Jersey Cancer Registry and Medicaid Research files provided diagnostic, prognostic, and treatment information on 237 black and 485 white women aged 20-64 years diagnosed with early stage breast cancer between January 1997 and December 2001. Racial differences in treatment and survival were examined using logistic regression and Cox proportional hazards models respectively. There were no differences in surgical, radiation, or adjuvant systemic treatment between blacks and whites. Breast cancer specific mortality (Hazard ratio (HR) = 1.37; 95% confidence interval (CI) = 0.94-1.98) and all-cause mortality (HR = 1.43; 95% CI = 1.08-1.89) were higher among blacks than whites. In this study of Medicaid-enrolled women with similar socioeconomic status and health care access, blacks and whites received similar breast cancer treatment. In spite of this, blacks had higher mortality than whites. Our findings suggest that factors other than treatment differences may contribute to the racial disparity in mortality.