The incidence of protein malnutrition was studied in 74 unselected patients with inflammatory bowel disease who were in the following categories: ileostomy (16), remission (15), elective surgery (12), acute attack (12), urgent surgery (10) and post-surgical complications (9). Compared with a control group, the patients in the urgent surgery group had low values for plasma albumin transferrin, pre-albumin and haemoglobin and these values were even lower in the patients who developed a major complication after surgery. There was no evidence of protein malnutrition in the ileostomy patients or in those in whom the disease was in remission. Nutritional therapy is strongly indicated in patients who are admitted to hospital with a severe attack of colitis and in whom urgent surgery is probable.