OBJECTIVES: To study 1-year treatment persistence among patients with rheumatoid arthritis (RA), initiating biologics (etanercept or adalimumab) with or without non-biologic disease modifying anti-rheumatic drugs (NbDMARDs). METHODS: Adult (≥18 years) patients with RA newly treated with etanercept or adalimumab with ≥360 days continuous enrolment before and after their first (index) biologic claim were identified in the MarketScan® Research Databases (Jan 1, 2010-Dec 31, 2011) and the Optum Research Database (Jan 1, 2009-Oct 1, 2011).  Patients with a claim for a biologic in the 360 days pre-index  or treated with biologics for conditions other than RA were excluded. Monotherapy patients met the following criteria at index:  1) Initiated monotherapy; no claim for a NbDMARD 360 days pre- and up to 30 days post-index or 2) Switched to monotherapy; ≥1 claim for a NbDMARD between day -360 and -30 (pre-index) and no claims for a NbDMARD between day -29 and +30. Combination therapy patients met the following criteria: 1) Initiated combination therapy; no claims for NbDMARDs from day -360 to -30 and ≥1 claim for a NbDMARD from day -29 to +30 or 2) Switched to combination therapy;  ≥1 claim for a NbDMARD between day -360 and -30, and another claim for a NbDMARD from day -29 to +30. Persistence was defined as the number of days from the index date until the earlier of a 45-day gap in therapy or a switch to another biologic. RESULTS: Of 6,626 patients in the MarketScan and 2,426 patients in the Optum databases, 35.7% and 36.9% were on biologic monotherapy respectively. Persistence was similar in both databases and higher with combination therapy (Truven/Optum: 45.1%/48.6% etanercept, 42.6%/47.0% adalimumab) than with monotherapy (Truven/Optum: 35.5%/43.1% etanercept, 35.1%/44.0% adalimumab). CONCLUSIONS: Combination therapy was associated with greater persistence than biologic monotherapy.