Forty-six years old male was admitted to our hospital because of urolithiasis, in 1968. Hyperuricemia was detected, and administration of allopurinol was started. From 1980, when he was 58 years old, to 1986, he underwent transrectal ultrasonotomography five times for screening of prostatic diseases. Diagnoses of the examinations were normal. In Nov. 1986, urinary retention was occurred. Needle biopsy of prostate disclosed adenocarcinoma. Castration was done, and postoperative transrectal ultrasonotomography showed decrease of the prostatic weight. We here present serial tomograms of the case, and stress the importance of the careful diagnosis based on the comparison with the past examination.