Five patients receiving maintenance peritoneal dialysis (duration, 3 mo.-4 yr) required surgical exploration of the abdomen for various reasons. Four had a prior history of bacterial peritonitis and 4 of aseptic peritonitis. At laparotomy, the peritoneal membrane was markedly thickened and sclerotic in all patients and loops of bowel were bound together in a dense, opaque casing. On microscopic examination, an increase in fibroconnective tissue in the peritoneum was observed.