Between January 1989 and March 2002, we treated 299 male bladder cancer patients and 416 prostatic cancer patients. Of these, 17 patients (5.7% of the male bladder cancer patients and 4.1% of the prostatic cancer patients) had double cancer consisting of prostatic cancer and bladder cancer. The mean age at diagnosis of the first and second cancer was 71.6 years and 75.5 years, respectively. Of the 8 patients with synchronous tumors, 3 patients had latent prostate cancer when they underwent total cystoprostatectomy. The mean interval between the first and second cancer was 45.3 months. The mean follow-up period was 84.7 months (ranged from 5 to 324 months) and two patients died of cancer (bladder: 1, prostate: 1). In the literature, the coincidence of bladder cancer and prostatic cancer is the highest in the urological field. In follow up of either of these cancer patients, it is important to be aware of not only progression of the first cancer but also generation of a second cancer.