In 16 patients with ulcerative colitis, total body fat, total body protein, and total body water were measured before and two weeks, three months, and twelve months after the establishment of an ileoanal J-pouch anastomosis. The 16 patients underwent elective surgery for their inflammatory bowel disease but were significantly protein depleted before surgery when their body composition was first measured. Twelve months later, all patients were in good health, back to work, and had normally functioning pouches (average stool frequency 4.3 ±1.4 per day). As a group, their stores of body protein and hydration state had returned to normal limits although their body fat stores were increased. Over the postoperative period there were significant losses of weight, protein, fat, fat-free mass, and total body water. These levels had returned to preoperative values (but not to normal) three months later. It is concluded that protein depleted patients with ulcerative colitis presenting for major surgery continue to have distorted body composition for several months after surgery but after approximately 12 months, when they have returned to work and feel well, body composition has returned to normal. © 1990 American Society of Colon and Rectal Surgeons.