PURPOSE: Resources for studying inflammatory bowel disease (IBD) are needed in evaluations of drug safety including traditional drugs and new biologics agents. We developed an IBD registry, with ascertainment from computerized visit information. OBJECTIVE: We sought to characterize the positive predictive value (PPV) of IBD case-finding using computerized data compared with chart review. METHODS: We identified 2906 persons aged 89 years or younger with one or more IBD diagnoses in computerized visit data during the period of 1996-2002. The diagnosis of IBD was confirmed through chart review. Adopting chart review as the gold standard, the validity of computerized encounter data to determine IBD was estimated. RESULTS: Among the 2906 study subjects with one or more ICD-9 diagnosis codes of 555 or 556 in computerized data, 81% were confirmed as having IBD by chart review. Defining cases as those who underwent two or more visits without regard to diagnostic procedures or drug utilization maximized the correct classification of cases (PPV, 95%). CONCLUSIONS: The quality of IBD diagnoses in computerized data is adequate to meet the aims of a wide range of research studies.