From 1981 through 1990, 21 urologic cancer cases were discovered in 21 uremic patients at our hospital. This constituted 55% (11 of 20) of the total malignancies in nondialyzed uremic patients, 41% (nine of 22) of the total in chronic hemodialysis patients, and 50% (one of two) of those in patients on continuous ambulatory peritoneal dialysis. No cases of urologic cancer were found in kidney transplant recipients. When compared with the general population, the standardized incidence ratio of kidney cancer in chronic hemodialysis patients was found to be 24.1 (P < 0.01) and that of bladder cancer was found to be 16.4 (P < 0.01). Multiple underlying renal diseases contributed to the development of the urologic cancer cases, including four analgesic nephropathy-associated transitional cell carcinoma cases, two acquired cystic kidney disease-associated renal cell carcinoma cases, two chronic pyelonephritis-associated (stone and tuberculosis) squamous cell carcinoma cases, and one xanthogranulomatous pyelonephritis-associated transitional cell carcinoma case. Uremia per se may be an important promoting factor. Hematuria (17 of 21 cases) was the most common presenting feature despite the fact that most of the patients were anuric. The clinical diagnosis of renal parenchymal tumors was based on ultrasonography (five of five cases), whereas most urothelial tumors were detected by cystoscopy or retrograde pyelography (14 of 16 cases). The survival rate of the 17 aggressively treated patients was 82% at 2 years and 45% at 5 years. We conclude that uremic patients are at greater risk of developing urologic cancer.(ABSTRACT TRUNCATED AT 250 WORDS)