AIM： To estimate the prevalence of celiac disease （CD） in adult patients with presumed irritable bowel syndrome （IBS）. METHODS： Between March 2005 and December 2008, 742 consecutive patients （293 male, median age 43 years, range 18-69 years） fulfilling the Rome Ⅱ criteria for IBS were prospectively enrolled in the study. IBS was diagnosed via self-completed Rome Ⅰ modular questionnaires. Anti-tissue transglutaminase （anti-tTG） serology was checked to initially recognize possible CD cases. Patients with a positive test were offered endoscopic duodenal biopsy to confirm the diagnosis of CD. RESULTS： Thirty two patients （15 male, median age 41 years, range 19-59 years） were found to have organic diseases other than CD. Twenty four patients tested positive for anti-tTG antibodies, and duodenal biopsies confirmed the diagnosis in all of them. Thus, in this patient population with presumed IBS, 3.23% actually had CD. CONCLUSION： CD is common in patients with presumed IBS. Routine screening for CD in patients with symptoms of IBS is recommended.