The fate of the contracted kidney in long-term hemodialysis patients was examined. Total kidney volume was measured by computer assisted tomography in 96 chronically hemodialyzed patients with chronic renal failure due to chronic glomerulonephritis. The presence of cysts and/or tumor in the renal parenchyma was evaluated. Kidney volume decreased progressively up to 3 years after the start of dialysis. However, after 4 years of dialysis, it then increased in a number of cases. Multiple cysts were found in 43.5% of patients on dialysis for less than 3 years and in 79.3% of patients who had been on dialysis for more than 3 years. They were found in 100% of those whose total kidney volume exceeded 50 ml despite more than 3 years dialysis. Bilateral nephrectomy was performed in 4 cases who had been dialyzed for more than 5 years and all showed acquired cystic disease of the kidney. Three out of 4 resected cases had adenocarcinoma and multiple adenomas in addition to acquired cystic disease of the kidneys. The other had intracystic epithelial hyperplasia. These results suggest that long-term hemodialysis is associated with a very high incidence of acquired cystic disease of the kidney. There is frequent enlargement of the contracted kidney, and a high incidence of renal adenocarcinoma in patients with glomerulonephritis leading to treatment with hemodialysis.