The epidemiology of prostate cancer gives us some clues that its etiology is likely both environmental and genetic. There is extreme country to country variability in prostate cancer mortality. Countries in which dietary fat intake is greater have been shown to have higher prostate cancer mortality rates leaving some to conclude that dietary fat causes prostate cancer. Migration studies show that men moving from Japan and China adopt increased risks of prostate cancer. Second- and third-generation Japanese Americans and Chinese Americans actually have risks of prostate cancer similar to white American men. This is highly suggestive that prostate cancer has an environmental influence. The differences in black-white mortality and newer data suggesting a higher mortality among Jamaican and Brazilian men of African descent suggest there may be a genetic predisposition to prostate cancer. Some have suggested certain polymorphisms increase prostate cancer risk, whereas others are searching for genetic mutations that may increase prostate cancer risk. Africans may have an increased prevalence of these genetic risk factors. Ultimately, the cause of prostate cancer is likely to be a combination of environmental and genetic factors.