Twenty patients with irritable bowel syndrome due to food intolerance were randomized to either oral sodium cromoglycate or placebo in a double-blind cross-over trial. The study consisted of treatment with either sodium cromoglycate or placebo for 8 weeks, followed by the cross-over treatment for 8 further weeks. Patients were allowed to eat the offending foods during the study. Eighteen patients completed the study. Analysis of patients' diary card scores showed a statistically significant difference in favour of sodium cromoglycate. There was a long carry-over effect in the active-placebo order group. Therefore oral sodium cromoglycate seems to be a useful treatment in patients with irritable bowel syndrome and proven food intolerance.