The staging, screening and diagnosis, and treatment of prostate cancer are discussed. Prostate cancer kills about 40,000 men in the United States each year. Signs and symptoms range from dysuria to features of advanced metastatic disease. The American Urological System of staging prostate cancer designates four stages, A through D. The tumor is graded histologically with the Gleason scale. Methods used in the screening and diagnosis of prostate cancer include digital rectal examination, the prostate-specific antigen (PSA) assay, biopsy, transrectal ultrasonography, and determination of PSA density, velocity, and age specificity. The value of screening and treatment remains controversial because tumors are generally slow-growing and conclusive data showing an effect on survival time are lacking. Treatment methods consist of prostatectomy, radiation therapy, and hormonal drug therapy or bilateral orchiectomy. The choice is influenced primarily by the stage of the disease but also by the patient's age, physical condition, and response to prior therapy. Patients with stage A or B disease are considered for prostatectomy or radiation therapy. The primary treatment for stage C disease is radiation therapy. For stage D, the main approaches are watchful waiting and bilateral orchiectomy or hormonal drug therapy to reduce androgenic stimulation of prostate tissue. Long-term survival rates are high for stages A and B and considerably lower for stages C and D. Prostate cancer responds to estrogens, but adverse effects are frequent and potentially severe. Luteinizing hormone-releasing hormone agonists (leuprolide and goserelin) are as effective as estrogens but have less toxicity; a disadvantage of these agents is an initial flaring of the disease. Other hormonal agents used include antiandrogens-progestins, flutamide, and bicalutamide. Secondary hormonal treatments (aminoglutethimide and ketoconazole) are less effective than initial hormonal therapy. Antineoplastic agents have little or no effectiveness in prostate cancer. Although the value of screening for and treating prostate cancer continues to be debated, many experts recommend annual screening for all men over 50. Research to identify more effective drugs for treating advanced disease continues.