We collected data on the histologic grade, stage, and age at diagnosis of 4,114 cases of prostate cancer (1,380 blacks, and 2,734 whites) in the Chicago area. The relationship between histologic grade (high = poorly or undifferentiated vs. low = well or moderately differentiated) and race (black vs. white) was examined using logistic regression. After adjusting for stage (localized, regional, and distant), the odds of high histologic grade prostate cancer in blacks compared to whites equaled 1.7 (95% CI [1.4, 2.0], P < 0.0001). These data suggest that blacks have a significantly higher burden of high histologic grade prostate cancer than whites, even after adjustment for stage at presentation. This higher burden may explain, in part, their higher mortality rate from prostate cancer given the U.S. black vs. white difference in prostate cancer mortality of a similar magnitude.