OBJECTIVES: The objectives of this study were to compare healthcare costs and switch rates between rheumatoid arthritis (RA) patients initiating intravenous (IV) abatacept, adalimumab, etanercept or infliximab.  METHODS:   This study was a retrospective analysis of administrative claims data from US managed care plans. Patients who initiated one of the following study biologic disease modifying antirheumatic drugs: IV abatacept, adalimumab, etanercept or infliximab were identified and date of initiation was defined as the index date.  The identification period was 7/1/2004 through 3/31/2010. Patients were required to have continuous eligibility in the 6 months pre-index (baseline) period and in the 12 months post-index (follow-up) period, were aged ≥18 years at index, and had ≥1 baseline medical claim with an ICD-9-CM diagnosis code for RA (714.0x, 714.2x). Outcomes evaluated in the 12 month follow-up period were total healthcare costs (medical + pharmacy) and switch rates. Generalized Estimating Equations were used to compare mean change from baseline in total healthcare costs between the treatment groups.  Logistic regression analysis was used to compare the odds of switching between treatment groups after controlling for baseline characteristics.  RESULTS: The study included 8505 first-line patients and 2181 second-line patients.  In first-line patients change from baseline in monthly total healthcare costs were higher for etanercept (Cost Ratio (CR)=1.26; p=0.0112), adalimumab (CR=1.30; p=0.0065) and infliximab (CR=1.10; p=0.3355) compared to abatacept.  In the first-line population, after controlling for baseline covariates, etanercept (Odds Ratio (OR)=2.52, 95% confidence interval (CI):1.57, 4.05), adalimumab (OR=2.33, 95% CI:1.44, 3.77) and infliximab (OR=1.91, 95% CI:1.17, 3.13) had significantly higher odds of switching compared to abatacept.  Results for the second-line population were consistent with results from the first line population.  CONCLUSIONS: First or second-line abatacept patients had lowest mean change from baseline in total healthcare costs and lower rates of switching compared to adalimumab, etanercept or infliximab patients.