The study revealed no correlation between steroid dosage and postoperative morbidity or mortality. The incidence of wound dehiscence and incisional hernia compared favourably with the reports of other unselected series of similar patients. Contamination did significantly influence results. Septic complications were more frequent when the operative field was contaminated and both delayed wound healing and mortality were related to this sepsis. A 'clean and dirty' technique was effective in controlling contamination during elective bowel division but preoperative bowel perforation and accidental entry into the lumen of the bowel during dissection were potentially avoidable sources of contamination. Primary healing of the perineal wound after proctocolectomy was seldom achieved in contaminated patients where a drain tube was brought out through the main perineal incision. When perineal sinuses or fistulae followed a proctocolectomy, patients with Crohn's disease had a significantly slower rate of healing than did patients with ulcerative colitis. However, there was no difference in the healing of abdominal wounds in relation to the primary pathology. Even abdominal incisions which were used on more than one occasion healed as well as those which were used for the first time. A prophylactic antibiotic regime of either ampicillin or tetracycline offered little protection against postoperative sepsis. The organisms which caused such infections were often insensitive to the two antibiotics.Corticosteroids are employed widely and often successfully to treat acute attacks of ulcerative colitis. They are also effective in improving the symptoms of patients with Crohn's disease of the colon, but in both diseases their use is often considered to be a major disadvantage if surgery becomes necessary, because they may increase the patients' susceptibility to infection (Fuenfer et al., 1973); they may retard healing (Erlich et al., 1973); and they may be the cause of other serious complications such as peptic ulceration (Glenn and Grafe, 1967). This paper reports the incidence and cause of such post-operative complications in a group of 107 patients who had surgery for ulcerative or Crohn's colitis under corticosteroid cover between January 1969 and December 1974.Received for publication 2 March 1978 Mlethods SUBJECTS A retrospective study of the case notes of colitic patients who were treated surgically in Oxford during this time was undertaken. If the following criteria were met:1. The prinary diagnosis was ulcerative colitis or Crohn's colitis.2. Prednisolone in a dose of 20 mg or more per day was administered during the operation and had been continued for at least five days postoperatively.3. All patients had undergone a singlestageproctocolectomy, or split ileostomy.4. A standard technique had been employed for each operation and the preoperative preparation and postoperative management had been standardised. Some of the patients had undergone more than one operation, and subsequicnt abdominal operations in 729 on 10 ...