OBJECTIVES: To determine whether differences existed in prostate cancer treatment received by white and African American men at a health maintenance organization where access to medical care is theoretically equal for all members and, if so, to determine the reasons for these differences. METHODS: We used information from the Kaiser Permanente Northwest Tumor Registry to identify all men diagnosed with local- or regional-stage prostate cancer between 1980 and 2000. We compared the likelihood of treatment with curative intent (TCI) between the two races, adjusting for age, tumor grade, stage, and the presence of comorbid conditions. We reviewed medical records of all 79 African American men and a sample of 158 white men (matched for age, stage, grade, and year of diagnosis) to determine the reasons that men did or did not receive TCI. RESULTS: Seventy-one percent of African American men and 82% of white men were treated with curative intent (P = 0.01). African American men were not more likely than white men to refuse TCI when it was offered (10.6% versus 8.1%, respectively; P = 0.6). However, urologists offered TCI less often to African American men than to white men (85% versus 91%, respectively; P = 0.02), and this difference could not be explained by differences in age, tumor grade, stage, or presence of comorbid conditions. CONCLUSIONS: African American men were less likely to receive TCI than white men. Because all of the men were insured, economic factors did not cause this difference. Furthermore, the cause did not seem to be differences in age, tumor grade, stage, or comorbid conditions.