BACKGROUND. African Americans (AA) have higher mortality from breast cancer compared with white Americans (WA). Studies using population-based cancer registries have attributed this to disparities in treatment after normalizing the AA and WA populations for differences in disease stage. However, those studies were hampered by lack of comorbidity data and limited information about systemic treatments. The objective of the current study was to investigate racial disparities in breast cancer treatment by conducting a comprehensive medical records review of women who were diagnosed with breast cancer at the Karmanos Cancer Institute (KCI) in Detroit, Michigan. METHODS. The study cohort consisted of 651 women who were diagnosed with primary breast cancer between 1990 and 1996 at KCI. Multivariable logistic regression analysis controlling for sociodemographic factors, tumor characteristics, comorbidities, and health insurance status was used to assess whether there were differences between WA and AA in the receipt of breast-conserving surgery (BCS), radiation, tamoxifen, and chemotherapy. RESULTS. There was no significant difference between WA and AA in the receipt of BCS versus mastectomy. Patients with local-stage disease who were enrolled in government insurance plans underwent mastectomy more often (vs BCS plus radiation) compared with patients who were enrolled in nongovernment plans. The rates of receipt of tamoxifen and chemotherapy were similar for local-stage WA and local-stage AA. However, WA were more likely to receive tamoxifen and/or chemotherapy for regional-stage disease. Married women with regional disease were more likely to receive chemotherapy than nonmarried women. CONCLUSIONS. The results from this study may be used to target educational interventions to improve the use of adjuvant therapies among AA women who have regional-stage disease. Cancer 2007 © 2007 American Cancer Society.