An intestinal permeability test analyzing the differential urinary elimination of lactulose and mannitol orally ingested at the same dosage was carried out first in fasting condition, then combined with specific food ingestion, in 17 children with clinical symptoms of irritable bowel syndrome (IBS). Foods were selected based on a suggestive clinical history or on a positive radioaller-gosorbent or prick test. Comparison of the results with those of a control population reported in a previous study showed that in nine IBS patients, specific food ingestion was associated with a modification of intestinal permeability. The nine children all had a personal and/or familial history of allergy and/or raised total IgE. The symptoms disappeared in the nine patients after food exclusion either alone (seven patients) or together with further treatment by cromolyn (two patients). We conclude that, at least in some children, symptoms of IBS may be related to food hypersensitivity.