Although there has been controversy about the early detection of prostate carcinoma by mass screening, we carried out an investigational study of such screening, using digital rectal examination (DRE) and serum prostate-specific antigen (PSA) determination in Hokkaido, Japan. We determined the detection rate and some profiles of the carcinoma detected by screening in Japanese men 50 years old and older. The detection rate of carcinoma was 1.10% in 1,639 participants. The rate linearly increased with aging from 0.25% for men in their fifties to 2.29% for those in their seventies. Two thirds of the carcinomas were T1(c) or T2, the frequency of which seemed to be higher than that of patients who visited medical institutions. The simultaneous use of both DRE and serum PSA determination showed a higher positive predictive value than either alone. Our current results indicated that the detection rate of carcinoma was higher than we previously anticipated for Japanese men, and that simultaneous use of DRE and serum PSA determination yielded a higher positive predictive value than either alone.