Males on long-term dialysis tend to develop more severe forms of acquired cystic disease of the kidney than females. The severity of the disease is unaffected by therapeutic modality, either hemodialysis or CAPD, however, cystic transformation becomes less extensive after successful renal transplantation. The fundamental pathological change characteristic of acquired cystic disease is epithelial hyperplasia, with the uremic milieu and duration of uremia being the most important factors in its development. Renal cell carcinoma, the most important complication of acquired renal cystic disease, has a high prevalence and incidence, usually remains symptomless and sometimes reveals metastases. Therefore, many clinicians and investigators, but not all, accept the need for regular screening of all dialysis patients for the development of renal cell carcinoma. Major complications of acquired renal cystic disease, malignancy and retroperitoneal bleeding, will become increasingly important because of the growing number of patients on long-term dialysis.