One hundred and eight patients with ileostomies were investigated for cholelithiasis at routine annual review in a large Ileostomy Clinic. Gallstones were demonstrated in 24-5%, which is three times the incidence that might have been expected in a population of this age and sex distribution. The frequency of cholelithiasis was significantly increased in those patients who had lost more than 10 cm of ileum at operation, regardless of whether the primary condition had been ulcerative colitis or Crohn's disease. It was significantly increased in those patients who had had a resection of less than 10 cm of ileum if the original condition had been Crohn's disease, but not if it had been colitis.