OBJECTIVES: To evaluate costs and clinical response of different treatments with biologic drugs for rheumatoid arthritis. METHODS: The study was designed as a prospective cohort. A sample of 15 patients was selected for analysis. Selection criteria: patients with RA with moderate to severe disease activity, failure to treatment with DMARDS and no previous use of anti-TNF drugs. The following parameters were considered in the calculation of direct costs: average doses, treatment duration, number of doses received and cost per milligram (mg) of each drug. The clinical outcome evaluated was DAS 28 at day zero and at 160 days. The criteria considered for low activity of disease was DAS 28 ≤ 3.2 and for remission DAS 28 ≤ 2.6. RESULTS: Among the 15 patients included, the average age was 45 years, 33% were men, with average BMI of 25.81kg/m², 73% with disease duration above 5 years, and average duration of treatment with DMARDs of 2.27 years. Among these, 3 patients were treated with Adalimumab (average dose: 40mg; R$75.13/mg; 6 doses); 3 with Etanercept (average dose: 50mg; R$28.28/mg; 15 doses) and 9 with Infliximab (average dose: 201mg; R$30.77/mg; 4 infusions). The average follow-up time was 16 weeks. Adalimumab resulted in an average cost of R$18031.41 with a 63% reduction in DAS 28 (2.03), presenting remission criteria. The average cost with Etanercept was R$21,209.55 with a 3% reduction in DAS 28 (5.31). Infliximab resulted in an average cost of R$ 24,766.11 with a reduction of 26% in DAS 28 (3.23) presenting criteria for low activity of disease. CONCLUSIONS: The first line treatment of patients with moderate to severe RA with Adalimumab presented the best clinical response in 160 days, achieving criteria for disease remission at the lowest treatment cost. The treatment with Etanercept resulted in the worst relation between cost and clinical response.