To determine if patients with bladder cancer have a higher incidence of unsuspected prostate cancer, 40 cases were studied. All except one case had no evidence of prostate cancer on preoperative clinical assessment. Detailed pathological evaluation of cystoprostatectomy specimens with sections at 2- to 3-mm intervals was done. Adenocarcinoma of the prostate was identified in 18 of 40 patients (45%). Multifocal prostatic intraepithelial neoplasia (PIN) was present in 19 cases (47.5%); 4 (10%) without an associated prostate cancer and 15 (37.5%) in conjunction with adenocarcinoma of the prostate. Twelve cases of unsuspected prostate cancer were stage pT1a, 4 were pT1b, and 2 were pT3. No patients exhibited nodal or distance metastases by the prostate cancer. At a mean follow-up of 15.2 months (range 3-34 months), 37 of the 40 patients are alive. Among prostate cancer patients, no clinical or biochemical evidence of disease recurrence or prostate cancer related mortality has been observed. Our findings support the previously reported high incidence rate of prostate cancer in patients undergoing cystoprostatectomy for bladder cancer. This, though, may not be higher than the observed incidence in an age-matched general population. We recommend DRE and PSA as part of the bladder cancer workup in males, and complete removal of the prostate at cystoprostatectomy to prevent the dilemma of residual prostate cancer.