OBJECTIVE: To assess the usefulness of health plan administrative data for identifying patients with irritable bowel syndrome (IBS). STUDY DESIGN AND SETTING: In this retrospective study of 442 medical records of patients in nine U.S. health plans, five sets of criteria that used administrative data were used to identify potential IBS patients. Physician reviewers provided an assessment of the likelihood of the diagnosis of IBS being present. IBS was considered to be present if the physician reviewer categorized the case as definite, probable, or possible based on medical record review. Analyses were also performed with cases categorized as possible placed in an "IBS not present" category. RESULTS: The positive predictive value (PPV) for the five sets of criteria ranged from 63% to 83% with the highest PPV found with one of the most restrictive criteria. When cases characterized as possible were included in the "IBS not present" category, the PPV for each of the five sets of criteria decreased substantially, ranging from 33% to 63%. CONCLUSION: The PPV of different criteria used to identify patients with IBS from administrative data varies substantially based on the criteria that are used. Use of criteria with a higher PPV may come at the expense of generalizability.