Ultrasonic examination of the kidney was performed on 280 patients undergoing chronic dialysis. Acquired cystic disease of the kidney (ACDK) was detected in 107 of 529 kidneys (20.2%). This paper presents an analysis of ultrasonotomograms of ACDK. Ultrasonic measurement of the size of ACDK was 72.5 +/- 15.2 mm in length and 41.7 +/- 9.8 mm in thickness. The size of ACDK was significantly greater than that of contracted kidneys by ultrasonographic diagnosis. With regard to sex distinction the length and thickness of ACDK were significantly greater in males than in females. As for laboratory data, patients with ACDK showed significantly higher values of red blood cell count, hematocrit and serum creatinine concentration compared with contracted kidneys. Prolongation of the dialysis peirod increased the incidence of ACDK. The size of ACDK showed a tendency to increase with duration of dialysis. However, no correlation was noted statistically between the incidence of ACDK and duration of dialysis and between the size of ACDK and duration of dialysis. There was a significantly lower incidence of ACDK in patients with diabetic nephropathy than those with chronic glomerulonephritis. A sonographic feature of ACDK is irregularity of the renal contour because of cystic transformation. Renal imaging, identification of the corticomedullary border, identification of the central echoes and increased parenchymal echogenicity were similar to other dialyzed kidneys. The main complications of ACDK are hemorrhage and tumor formation. We observed two retroperitoneal hematomas and one renal cell carcinoma developed within two years after this examination. The incidence of complications of ACDK was 5.1 per cent. We believe that patients with ACDK should be watched carefully by regular ultrasonic examination for early diagnosis and treatment of these complications.