Adenocarcinoma of the prostate is the most frequently diagnosed cancer and the second leading cause of cancer deaths among American men. Prostate cancer has an even more devastating impact on the African American community: African American men have the highest incidence of prostate cancer in the world. At diagnosis, these patients are significantly younger in age and demonstrate a more advanced stage of the disease than Caucasian men. The mortality rate of prostate cancer is approximately 50% higher among African American men than among Caucasian men. Although there is mounting clinical evidence that the etiology of prostate cancer in African American men differs from that in Caucasian men, there is little understanding of the underlying molecular mechanisms. Complementary DNA microarrays allow the simultaneous assessment of thousands of genes in order to determine if there is a differential gene expression pattern that consistently segregates according to race and tumor grade. This microarray study compares total RNA samples extracted from histologically graded and Gleason-scored tumor prostectomy specimens from 20 African American and 10 Caucasian cancer patients.