In 45 of 165 male cystectomy patients with bladder cancer (27 per cent) incidental adenocarcinoma of the prostate was found during the diagnostic evaluation or histological examination of the cystoprostatectomy specimens. Of the patients 37 had stage A1 or A2 and 8 had stage C or D1 prostate cancer. Clinical presentation, stage and grade distributions for each primary and prognostic variable are reviewed. Over-all, 67 per cent of the patients currently are alive with a 3-year actuarial survival rate of 60 per cent. The presence of incidental stage C or D1 prostate cancer in the surgical specimen implies incomplete surgical excision and it may warrant additional postoperative treatment. However, a significantly increased mortality rate among these patients has not been identified during the limited median followup of 25 months.