OBJECTIVES: Nonsteroidal antiinflammatory drugs (NSAIDs) are in widespread use for rheumatic diseases in Mexico, but can cause peptic ulcers and gastrointestinal bleeding and perforation. The purpose of this study was to evaluate cost – effectiveness ratios of celecoxib compared with NSAIDs and acetaminophen in adult patients with osteoarthritis in four hospitals in the Social Security Mexican Institute. METHODS: A decision tree model was developed using a Bayesian approach. The model simulated treatment of a hypothetical cohort of 1000 patients diagnosed with osteoarthritis during a time horizon of 6 months. Patients could initiate treatment with celecoxib, NSAIDs (diclofenac, naproxen) and acetaminophen. Conditional probabilities of the model were obtained from published clinical trials and were complemented with Mexican expert opinion surveys. Effectiveness measure was the number of patients with articular pain controlled without adverse events (peptic ulcers, gastrointestinal bleeding, and others). The analysis was conducted from the healthcare payer's perspective. Resource use and costs were obtained from hospital records and Mexican official databases. Threshold and probabilistic sensitivity analysis was performed and acceptability curves were constructed. RESULTS: The model indicates that the use of celecoxib could lead to the avoidance of a significant number of adverse events associated to NSAIDs and acetaminophen. Celecoxib showed on the six-months period similar (p=0.52) expected costs per patient (US$609.8) than the treatment with NSAIDs (US$615.6) and lower costs (p<0.01) compared with acetaminophen (US$656.7). On the other hand, celecoxib was associated with higher effectiveness (371 patients, CI 95% 255-452) followed by NSAIDs and acetaminophen (274 and 270 patients, respectively). Results were robust to Monte Carlo first order sensitivity analysis. Acceptability curves showed the same results with a mean of 44.5% of certainty. CONCLUSIONS: Despite its higher cost in the Mexican market, celecoxib was cost – effective for the management of articular pain in patients with ostheoarthritis.