Renal ultrasound scanning was performed in 100 patients with end-stage renal failure treated by both haemodialysis and continuous ambulatory peritoneal dialysis (CAPD). Each kidney was assessed for the presence of acquired cystic disease and solid lesions. The appearances were divided into five grades from grade 0 (no cysts detected) to grade 4 (greater than 15 cysts per kidney). Other intra-abdominal organs were also scanned for the presence of cysts. The findings were then correlated with possible aetiological factors, including the type of dialysis used. Sixty-three percent of all the patients had acquired cystic disease of the kidney (ACDK). No solid lesions were found and no cysts were detectable in other organs. The presence and grade of ACDK did not correlate with the age or sex of the patient, the nature of the underlying renal disease, or the duration of chronic renal failure. There was a significant correlation between the grade of ACDK and the duration of both haemodialysis (P less than 0.001) and CAPD (P less than 0.01). The presence of residual renal function did not influence the development of cysts. ACDK had no effect on haemoglobin or other laboratory parameters measured.