Ultrasonograms of 546 kidneys were obtained in 280 patients undergoing chronic dialysis. Dialysed kidneys could be detected in 529 of the 546 kidneys (96.9%) by ultrasonic examination. The ultrasonic diagnoses on dialysed kidneys were contracted kidney in 313 kidneys (59.2%) and acquired cystic disease of the kidney in 107 kidneys (20.2%). Ultrasonic measurement of the size of kidney (length and thickness) revealed that the kidneys in patients with chronic renal failure were much smaller than normal ones. But the kidneys in patients undergoing dialysis for more than 8 years gradually increased in size with incidence of acquired renal cysts. The kidneys in patients with diabetic nephropathy were greater in length and thickness than those with chronic glomerulonephritis. Sonographic features of dialysed kidneys were unclear renal imaging, unidentified central echoes, cortico-medulla + border and increased parenchymal echogenicity. Irregularity of the renal contour had a tendency to increase in number with incidence of cysts in long-term dialysis patients. The ultrasonograms of the kidneys with diabetic nephropathy showed fewer changes than normal ones. No major complication of the kidney was detected in the present study. However, two retroperitoneal hematomas and one renal cell carcinoma developed within two years after this examination. We believe that regular screening of the kidneys by ultrasonic examination is mandatory in patients on chronic dialysis for early diagnosis and treatment of these complications.