OBJECTIVES: Anti-TNF-a drugs (Biologics) have become a cornerstone in the treatment of Rheumatoid Arthritis (RA). Since initial choice of agents is sometimes driven by expected treatment costs and related cost-effectiveness, we assessed the cost-effectiveness of Etanercept (ETA) and Infliximab (INF) based on published real-world data from the German Biologics Registry. METHODS: We designed an excel-based cost-effectiveness model and calculated the costs per LUNDEX responder month. The LUNDEX score developed by Kristensen et al. (2006) is combining the proportion of patients fulfilling a selected response criterion (e.g. ACR 20) with the proportion of patients adhering to a therapy. Our model compares the costs per LUNDEX-response over six months for the treatment with ETA and INF from a payer-perspective and calculates the cost per LUNDEX responder month. ACR 20 response rates (INF=46%; ETA=58%), adherence to therapy (INF=77%, ETA=82%) and real-world dosing data (INF=4mg/kg body weight, ETA=47.5mg/week) were derived from published registry data. Drug costs were calculated based on list prices. Administration and lab costs were derived from official databases. RESULTS: During the first six months, treatment with INF or ETA causes costs of EUR 10.873 € and EUR 9.683 €, respectively. The LUNDEX index at six months is 0.357for INF and 0.477 for ETA. Accordingly, the costs per LUNDEX response are 30.277 € for INF and 20.167 € for ETA. The average cost per LUNDEX-responder month in Germany is 5.033 € for INF and 3.362€ for ETA during the first six months of treatment. CONCLUSION: ETA is more cost-effective than INF in a real-world setting in Germany. Our cost-effectiveness analysis supports decision making based on a combined measure of response and therapy adherence. Long-term data on both response and adherence are needed to further assess real-world cost-effectiveness of Biologics.