Sclerosing peritonitis is a well-known complication of continuous ambulatory peritoneal dialysis (CAPD). Here we attempt to clarify the usefulness of ultrasound (US) in the diagnosis of this disorder. Fourteen patients with sclerosing peritonitis, 10 with minimal or no complaints (mild cases) and 4 caes with severe complaints (severe cases), were examined by US employing a 3.0-to-3 5 MHz convex trarsducer and by CT. Minimal intraperitoneal echogenic strands were demonstrated within the dialysate solution in the subphrenic space in all 10 cases of mild sclerosing peritonitis. In the four severe cases, prominent intraperitoneal echogenic strands were demonstrated within the dialysate solution in the lower abdomen. Minimal echogenic strands within the decreasing dialysate solution were demonstrated in the subphrenic space, however. In severe cases, abnormal distribution of ascites and thickening peritoneum covering the matted bowel were also visualized. On CT examination, a network pattern corresponding to the ecogenic strands was poorly demonstrated in one severe case, although abnormal distribution of dialysate solution and thickening of the peritoneum were clearly demonstrated in all four severe cases. We conclude that ultrasound exmination is more useful than CT for evaluating sclerosing peritonitis, especially in mild cases.