OBJECTIVES: Anti-tumour necrosis factor inhibitor (anti-TNF) therapy has been widely and successfully used in patients with rheumatoid arthritis (RA). However, about 30% of these patients have an inadequate response to these medicines. Abatacept has shown significant clinical and functional benefits in patients who have inadequate response to anti-TNF therapy. The aim of this analysis is to examine the cost-effectiveness of abatacept after the failure of a first anti-TNF. METHODS: A patient simulation model was constructed using clinical data from the (abatacept) ATTAIN trial and the British Society for Rheumatology Biologics Register (BSRBR).  The time horizon of this model was lifetime. Clinical effectiveness was evaluated by changes in Health Assessment Questionnaire (HAQ) score from baseline up to 12 months. Patients discontinued treatment due to a lack of efficacy or adverse events. After treatment discontinuation, patients received supportive care, regardless of treatment group. Utilities were obtained by mapping HAQ to EQ-5D. Cost inputs included drug and administration, monitoring, medical costs associated with HAQ level, and joint replacement costs obtained from published literature and inflated to 2009 British pounds. RESULTS: Abatacept was estimated to yield 1.06 additional quality-adjusted life years (QALYs) per patient (3.28 vs. 2.22) over a lifetime, compared to conventional DMARDs. The total lifetime costs associated with abatacept were ₤46,522 and total costs for conventional DMARDs were ₤17,025, resulting in an incremental cost-effectiveness ratio (ICER) of ₤27,936 per QALY gained.  Probabilistic and univariate sensitivity analyses confirmed the robustness of our findings. CONCLUSIONS: Abatacept is a cost-effective treatment option for patients with RA after the failure of a first anti-TNF in the UK.