Nutritional factors relative to IBS include diagnostic and therapeutic considerations. Etiologically, foods do not cause IBS. A small percentage of patients with childhood allergic diatheses, usually in association with atopic dermatitis and asthma, may be intolerant to one or more of wheat, corn, dairy products, coffee, tea, or citrus fruits. Diagnostically, many patients labeled as IBS subjects are in fact intolerant to the ingestion of lactose-containing foods, sorbitol, fructose, or combinations of fructose and sorbitol. A precise dietary history will characterize this group. Taken in its broadest context, IBS involves the entire hollow tract inclusive of esophagus, stomach, small bowel, and colon. The symptomatic presentation relative to the hollow organ involved allows the selection of dietary manipulations that may help to reduce symptoms. Gastroesophageal reflux, a consequence of low LES pressure in some IBS patients, may be treated with the elimination of fatty foods, alcohol, chocolate, and peppermint. Delayed gastric emptying may be helped by the elimination of fatty foods and reduction of soluble fiber. Aberrant small bowel motor function may be ameliorated by reduction of lactose, sorbitol, and fructose and the addition of soluble fiber. Gas syndromes may be improved by reduced intake of beans, cabbage, lentils, legumes, apples, grapes, and raisins. Colonic motor dysfunction may be overcome by the gradual addition of combinations of soluble and insoluble fiber-containing foods and supplements. The selective use of activated charcoal and simethicone may be helpful.