1. People with an ileostomy experience digestive problems with some foods. Why those foods are avoided is not known nor is it certain whether this interferes with the nutritional adequacy of their diet. 2. A detailed dietary assessment has therefore been made of thirty-seven subjects with ileostomies and a similar number of age- and sex-matched healthy controls. All food and drink eaten over 1 week was weighed and recorded. In addition. A larger group of seventy-nine ileostomy subjects and seventy matched controls answered a questionnaire designed to identify foods which upset them and which they avoided. 3. Total nutrient and energy intakes were similar in the two groups but the subjects with an ileostomy ate less dietary fibre (g/d; mean + SD: ileostomy subjects 18.0 +/- 5.9, controls 20.9 +/- 5.5; P less than 0.05) mainly due to lower fruit and vegetable intakes. Iron and vitamins A and C intakes were also less. 4. A majority of ileostomy subjects had a pattern of food intake different from the controls, taking more of their energy in the morning and less at night. A variety of food items upset more than half of them including nuts, pips, seeds, skins, onions, beetroot, lettuce, raw cabbage and carrot, peas, sweetcorn, mushrooms and dried fruit. 5. On the basis of the results it is possible to formulate general dietary advice for people with an ileostomy.