Prostate cancer is now the most common cancer and the second most common cause of death from cancer among men. Several studies have shown a frequency of autopsy-detected cancer of 40% in men over 50 years of age. In contrast, the lifetime probability of prostate cancer being diagnosed clinically is only 8%. Thus histologically documented prostate cancer only becomes clinically relevant if the tumors are > 0.5 cm3 and the life expectancy exceeds 10 years. Therapy with curative intention is only possible for organ confined disease. Because disease specific survival is about 80-90% after 10 years for conservative treatment of organ confined disease, early detection of prostate cancer is useful for patients with a life expectancy > 10 years. Organ confined prostate cancer is usually asymptomatic. The use of prostate specific antigen (PSA) combined with digital rectal examination (DRE) results in a 2-3 fold increase in prostatic carcinoma detection rate, especially of organ confined disease, by PSA. In men with a minimally elevated PSA-value of 4-10 ng/ml (Hybritech Assays), 25% will have a prostatic carcinoma regardless of the finding of the DRE, which would have reached clinical significance in the follow-up. The indication for biopsy should be established at an early date. There is no support for the common opinion that early detection programs detect clinically unimportant cancers. 95% of tumor volumes are > 0.5 cm3. Furthermore only 3-5% of subjects show prostate cancer in detection programs though 8% will develop clinical symptoms of prostate cancer during their lifetime. This difference is a reason for longitudinal programs with PSA and DRE control once a year, as proposed by the American Cancer Society and the American and Canadian Urological Association, in contrast to other health care organizations, which would wait with general screening until data from prospective randomized trials with beneficial effects of screening are available. To introduce prostate cancer therapy with curative intention for symptomatic patients as well, the cancer should be detected below a PSA level of 10 ng/ml. Insufficient specificity of PSA (2-4 patients have to undergo biopsies to detect one cancer patient) is still an unsolved problem.