An early detection study for prostate cancer was initiated to determine the effect of routine digital rectal examinations on the stage of prostate cancer at diagnosis. A prostate biopsy was recommended if induration, asymmetry or nodules were detected on the digital examination. During a 6-year period 4,160 examinations were performed on 2,131 men more than 45 years old. A prostate biopsy was performed on 144 men and 36 malignant tumors were detected, of which 68 per cent were clinically localized. Pelvic lymph node metastases were found in 6 per cent of the surgically staged cancer patients and in 10 per cent of the patients who had a high grade tumor. Surgical staging revealed that 50 per cent of the patients with clinical stage B disease were upstaged to stage C or D1 disease. These results suggest that mass screening programs using digital examination may not add sufficient benefit over conventional medical care to warrant the expense. Definitive proof that screening can lower the mortality rate from prostate cancer can be obtained only by a prospective randomized clinical trial.