To review the current state of knowledge regarding risk factors for prostate cancer. Analysis of the literature through the use of MEDLINE as well as identification of papers through review of article bibliographies and the authors' personal files. Current data were also extracted from the Surveillance, Epidemiology, and End Results Program (SEER) database. A review of risk factors for the development of prostate cancer. Emphasis was placed on identifying larger, controlled studies. The clinical incidence of prostate cancer is increasing. Risk factors for prostate cancer appear to include age, race, positive family history, vasectomy, and dietary fat intake. It appears that prostate cancer results from an interplay between endogenous hormones and environmental influences that include, most prominently, dietary fat.