BACKGROUND: Information on infliximab use in a community setting is important to understand patterns of medication use and to anticipate and plan for costs associated with the drug. We sought to understand predictors of initiation and discontinuation of infliximab in the community-based setting of Kaiser Permanente, Northern California, which provides integrated care to its members. METHODS: The cohort study was set during 1998-2006. Predictors of initiation were assessed among 494 Crohn’s disease (CD) patients who initiated infliximab and 2470 CD patients who did not initiate infliximab (controls). Data were obtained through linkage of computerized clinical information and were analyzed using logistic regression and Cox survival analysis. RESULTS: Infliximab infusions have increased rapidly since 2001, with no evidence of leveling off. Initiators were appreciably younger than controls (P < 0.001), but were similar to controls with respect to sex and race/ethnicity. The presence of at least 1 comorbidity was related to a modest increase in the risk of initiating (compared with none: 1 comorbidity, odds ratio [OR] = 1.52 with 95% confidence interval [CI] 1.16-2.00; 2 comorbidities, OR = 1.38 with CI 0.89-2.13). By 3 years after initiating, only 20% of patients remained on infliximab. CONCLUSIONS: In a community-based setting infliximab use has steadily increased. Age and comorbidity are associated with initiation, but sex and race/ethnicity are not. More information is needed to determine why, in this community-based setting, a large number of patients on infliximab discontinued their treatment.(Inflamm Bowel Dis 2008).