Five patients receiving maintenance peritoneal dialysis (duration, three months to four years) required surgical exploration of the abdomen for various reasons. Four had a prior history of bacterial peritonitis, and four of aseptic peritonitis. At laparotomy, the peritoneal membrane was found to be 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.