Jemal A, et al. - Nonelderly black and white women diagnosed with early-stage breast cancer were compared to determine the contribution of differences in demographics, comorbidity, insurance, tumor characteristics, and treatment to the overall mortality disparity. In this work, matching by insurance explained one-third of the excess risk of death among nonelderly black women; matching by tumor characteristics explained approximately one-fifth of the excess risk. A substantial decrease in ethnic/racial disparities in overall survival among these women could be achieved with efforts focusing on equalization of access to care.