The long-term goal is the development of preventive or therapeutic measures for benign prostatic hyperplasia (BPH). The principal specific aim is to evaluate the relations of the hormone profile to surgery to BPH. This aim will be met by a "nested" case-control analysis of blood specimens and other data collected in the Physicians' Health Study (PHS). The PHS is a randomized trial of aspirin and beta-carotene in the prevention of cardiovascular mortality and cancer incidence, conducted among U.S male physicians 40-84 years of age. The subjects completed questionnaires at entry, and follow-up has been done by use of questionnaires at 6 months, 12 months, and annually thereafter. As part of the trial, blood samples were collected before randomization and stored t -82 C. The specimens for 400 participants who had surgery for BPH and 400 controls will be retrieved and analyzed for testosterone, dihydrotestosterone, delta4-androstenedione, estrone, and estradiol. Mean hormone levels will be compared between cases and controls, and the relative incidence of surgically-confirmed BPH will be estimated according to quintiles of hormone levels. The secondary aim of the study is to evaluate the associations of BPH with cigarette smoking and components of the diet, especially beta-carotene and fat intake. This aim will be met by use of data collected on the entry and follow-up questionnaires on all 22,071 participants.