Forty-two patients with a bladder tumour and 4 patients with a ureteral tumour and a history of abuse of phenacetin-containing analgesics were studied. The sex ratio was 1:1, and the mean age 63 years. The estimated amount of ingested phenacetin was 7.1 kg, the estimated mean exposure time 21 years, and the estimated mean induction time 30 years. Renal papillary necrosis and impaired renal function were found in 34 patients. A history of recurrent urinary tract infection was found in 80 per cent of the patients, suggesting that the combination of phenacetin-abuse and chronic inflammation might be responsible for the localization of the tumours to the bladder. The majority of the bladder tumours were of low grade (1 and 2); muscular invasion was seldom found and metastases were rare. The patients were followed for 1.5-13 years. Twenty-six patients died; the mean survival time was 46 months. Uremia due to analgesic nephropathy was the main cause of death in 14 patients and contributed to death in another 7 patients. Three of the patients with ureteral tumours had received radiological treatment against the pelvic region, 15-20 years prior to the diagnosis of the ureteral tumour.