The development of multiple cysts in the previously noncystic chronically diseased kidneys of patients undergoing long-term dialysis appears to be associated with spontaneous renal bleeding and benign and malignant renal tumors. Two cases of acquired cystic disease with renal hemorrhage and adenocarcinoma are presented; metastases occurred in one patient and the other had bilateral carcinoma requiring bilateral nephrectomy. Combined data from 13 studies indicate acquired cystic disease occurs in one third of patients undergoing maintenance hemodialysis and is associated with adenocarcinoma in 4 percent of cases. Four cases of metastases and five deaths linked to acquired cystic disease have been reported. Eight of 24 patients with acquired cystic disease and clinical manifestations of renal bleeding had renal adenocarcinoma. Autopsy series indicate tumors associated with acquired cystic disease are usually benign but commonly bilateral and multiple. Cystic transformation of the end-stage kidney is more frequent after several years of hemodialysis. It is suggested that patients receiving dialysis treatments for more than three years have a baseline radiologic examination of the kidneys so that subsequent problems can be more easily identified and evaluated.