The incidence of a subsequent primary cancer was investigated among 10,014 patients with cancer of the urinary bladder diagnosed in 1953-1989 in Finland. During the follow-up period of 1953-1989, 652 new metachronous cancers were diagnosed. The number equals the expected number based on the national incidence figures. There were 195 second cancers of the lung. The standardised incidence ratio (SIR) for lung cancer was 1.3 among males [95% confidence interval (CI) 1.1-1.4] and 2.6 among females (95% CI 1.4-4.5). An increased SIR for larynx cancer in males (SIR = 1.7, 95% CI 0.91-2.8) and for kidney cancer in females (SIR = 3.6, 95% CI 1.8-6.2) was observed. The risk of a second cancer was greater among patients less than 60 years of age at the time of first diagnosis than among older patients. No consistent differences were observed in the risk of new cancer between bladder cancer patients treated with or without radiotherapy.