OBJECTIVES: Determine the cost-effectiveness of abatacept or tocilizumab in patients with rheumatoid arthritis (RA) with inadequate response to methotrexate (IR-MTX) in Colombia. METHODS: A patient-level simulation based on the Birmingham Rheumatoid Arthritis Model was adapted to the clinical practice patterns and demographic characteristics of the patients and validated by clinical experts in Colombia. The functional disability was assessed using the Health Assessment Questionnaire (HAQ); the mean scores and the distribution were derived from subjects screened to participate in clinical trials in Latin America. The effect of biologic therapy was assessed using changes in HAQ scores for the first 6 months based on a mixed treatment comparison and then projected over time. Direct medical costs were calculated from private and public providers, and the information system of the Ministry of Social Protection (SISMED).  A 20-year time horizon and the payer’s perspective were assumed. Costs and health outcomes were discounted at 3% annually. Sensitivity analyses were performed to the main parameters of the model. RESULTS: A hypothetical cohort of 1,000 patients with RA - IR MTX followed for 20 years or until death, the mean direct medical costs per patient for abatacept were U$132,654 (129,198-145,203), compared to U$283,753 (275,809-315,551) for tocilizumab. For the group of subjects treated with abatacept, 84% of these costs were associated with the drug; for tocilizumab, 93% of the costs are associated with the drug.  The mean number of life years were 29.27 (28.45-30.15) and 29.25 (28.43-30.13) for abatacept and tolicizumab respectively. The mean number of QALYs (discounted) by abatacept, and tocilizumab were: 7.21 (7.02-7.42), and 7.15 (6.96-7.37) respectively. Using abatacept as the reference treatment, tolicizumab provided less utility at a higher cost, being dominated by abatacept CONCLUSIONS: For the treatment of RA in patients with IR MTX in Colombia, the use of abatacept, as the reference treatment, is dominant over  tocilizumab.