Purpose The aim of this analysis was to implement a claims-based algorithm to estimate biologic cost per effectively treated patient for biologics approved for moderate to severe rheumatoid arthritis (RA). Methods This retrospective analysis included commercially insured adults (aged 18-63 years) with RA in a commercial database, who initiated biologic treatment with abatacept, adalimumab, etanercept, golimumab, or infliximab between 2007 and 2010. The algorithm defined effectiveness as having all of the following: high adherence, no biologic dose increase, no biologic switching, no new nonbiologic disease-modifying antirheumatic drug, no increased or new oral glucocorticoid use, and no more than 1 glucocorticoid injection. For each biologic, cost per effectively treated patient was defined as total drug and administration costs (from allowed amounts on claims), divided by the number of patients categorized as effectively treated. Findings Of 15,351 patients, 12,018 (78.3%) were women, and the mean (SD) age was 49.7 (9.6) years. The algorithm categorized treatment as effective in the first year for 30% (1899/6374) of etanercept, 30% (1396/4661) of adalimumab, 20% (560/2765) of infliximab, 27% (361/1338) of abatacept, and 29% (62/213) of golimumab treated patients. The 1-year biologic cost per effectively treated patient, as defined by the algorithm, was nominally lower for subcutaneously injected biologics than for infused biologics. The 1-year biologic cost per effectively treated patient, as defined by the algorithm, was lowest for etanercept ($49,952), followed by golimumab ($50,189), adalimumab ($52,858), abatacept ($71,866), and infliximab ($104,333). Implications Algorithm-defined effectiveness was similar for biologics other than infliximab. The 1-year biologic cost per effectively treated patient, as defined by the algorithm, was nominally lower for subcutaneously injected biologics than for infused biologics. © 2014 Elsevier HS Journals, Inc. All rights reserved.