Summary Background : Coeliac disease may easily mimic symptoms which are parts of the criteria used for diagnosing irritable bowel syndrome. Aim : To find the frequency of coeliac disease among patients diagnosed as irritable bowel syndrome. Methods : During a period of one year, irritable bowel syndrome patients referred to a university clinic in Tehran were studied. For each patient, an asymptomatic sibling was enrolled as control. Serological tests for coeliac disease were performed in all patients and controls. If positive, duodenal biopsy was performed to confirm the diagnosis. Patients subsequently diagnosed as coeliac disease were placed on a gluten free diet and re‐evaluated after 6 months. Results : One hundred and five cases of irritable bowel syndrome and 105 controls were enrolled. Coeliac disease was diagnosed in 12 of the irritable bowel syndrome patients and none of the controls. Eleven coeliac disease patients adhered to a gluten free diet. After 6 months, all 11 patients had significant improvement in symptoms and three were totally asymptomatic. Six allowed repeated endoscopy after 6 months of gluten free diet, of which five showed improvement in histological findings. Conclusions : Coeliac disease is a common finding among patients labelled as irritable bowel syndrome. In this sub‐group, a gluten free diet may lead to a significant improvement in symptoms. Routine testing for coeliac disease may be indicated in all patients being evaluated for irritable bowel syndrome.

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