Objective: To determine the annual drug and administration costs and dosage patterns for patients with rheumatoid arthritis (RA) treated with infliximab or abatacept from a managed care perspective. Methods: A retrospective analysis of medical claims was performed using the PharMetrics claims database. Patients with RA were identified from Janaury 1, 2003-December 31, 2005 for those prescribed infliximab and February 1, 2006-December 31, 2006 for those prescribed abatacept as first or subsequent biologic treatment. Patients were followed until medication switch, discontinuation, or end of study period. Primary outcomes of interest were annual drug and administration costs and dose escalation (increase in dose, dosing frequency or both). Patients' weight information required to calculate dose were unavailable, therefore paid amounts were used as proxy for dose. Results: From first to last infusion, patients receiving infliximab (n=1913) as first or subsequent biologic experienced an average dose increase of 17% and 39%, respectively. A total of 58% and 73% patients prescribed infliximab as first or second-plus biologic experienced dose escalation, respectively. For patients receiving abatacept (n=184) as first or subsequent biologic, dose increase averaged 1.2% and 6.5%, respectively (no increase in number of vials for either). The dosing interval for patients receiving abatacept followed the recommended dosing regimen. Patients treated with infliximab experienced an increase in dosing frequency, averaging 49 days earlier in treatment (from 4th to 14th infusion) and 33 days later in treatment (15th to last infusion). The estimated annual drug plus infusion administration cost of first and subsequent biologic therapy was $13,354 and $14,465 for abatacept and $16,608 and $23,913 for infliximab, respectively. Conclusion: Patients treated with infliximab experienced an increase in dosage and/or dosing frequency, resulting in an increase in real world treatment costs. Patients treated with abatacept showed no considerable increase in dose or dosing frequency from first to last infusion.