Simultaneous presentation of transitional cell carcinoma of the bladder and adenocarcinoma of the prostate is not uncommon. Twenty-two patients were diagnosed as having simultaneous or concurrent presentation of prostate and bladder carcinomas between January 1970 and July 1986. The overall five-year survival was 40 percent, with patients presenting with prostate cancer doing better (50%) than those with bladder cancer (32%). Retrospective review of these cases suggests that primary therapy should be directed to the most advanced cancer. Incidental prostate cancer may be "cured" with a cystoprostatectomy and, when indicated, radiation therapy added postoperatively for the bladder cancer. Eleven patients presented with Stage A prostate cancer: 10 of the 11 were treated for their bladder cancer. Treatment was usually radical cystoprostatectomy with or without postoperative radiation. None died of prostate cancer. Patients presenting with advanced stage prostate cancer have had recurrence or have died of the cancer.