Severe bowel dysfunction developed in 25 of 945 patients receiving long-term hemodialysis during a ten-year period. Colonic perforation occurred in 12 patients, six of whom died due to peritonitis. In seven instances, the perforation occurred spontaneously. Ten other individuals exhibited prolonged, severe adynamic ileus that progressed to colonic pseudo-obstruction in eight patients. Medical decompression (eight patients) and surgical bowel decompression (two patients) resulted in recovery in nine. Aluminum hydroxide gel, which was taken regularly by all patients, was associated with notable chronic constipation prior to the occurrence of bowel perforation or protracted adynamic ileus in 78% of these individuals. © 1982, American Medical Association. All rights reserved.