A prostate mass screening was performed in 6 towns in Shiribeshi area in Hokkaido Prefecture on 384 males who were over 50 years old. The screening included digital palpation, uroflowmetry, blood sampling for tumor markers, questionnaire for voiding disturbances and transrectal sonography. Prostatic carcinoma was found in 9 (2.3%) of 384 males. An incidence of benign prostatic hypertrophy was 15.6% in 384 males. Atypical hyperplasia was found in 4 among 35 biopsied cases. Incidence of voiding disturbance such as retardation, prolongation and nocturia significantly increased with age as well as prostate size.