OBJECTIVES: To evaluate the cost-effectiveness, from the Mexican Health Care System perspective, of Truvada versus Combivir and Kivexa in the treatment of antiretroviral naïve HIV-1 infected patients METHODS: A Markov model was developed to assess the incremental cost effectiveness of Truvada vs Combivir and Kivexa. Clinical data was derived from published clinical trials (Study 903 and CNA30024) and other secondary sources to create a model of disease progression and treatment patterns. Both healthcare and treatment costs were considered. Costs were reported in 2008 US dollar. Costs and health outcomes were discounted at 5%. A second-order probabilistic Monte Carlo sensitivity analysis was conducted to assess the effects of parameter uncertainty on the study findings. RESULTS: The model projects an accumulated discounted cost to the Mexican health care system per patient receiving the Truvada regimen of US$28,776 compared to US$24,605 for the Kivexa regimen and US$22,999 for the Combivir regimen. The accumulated discounted effect is 5.85 QALYs per patient receiving Truvada compared to 4.89 QALYs for Kivexa and 4.81 QALYs for Combivir. This results in an incremental cost for Truvada and Kivexa vs. Combivir of US$5,805 per QALY and US$19,436 per QALY respectively. Considering a willingness to pay (WTP) threshold of $US 10, 000 per QALY there is a 90% probability that treatment with Truvada is cost-effective relative to Combivir CONCLUSIONS: Results from these analyses suggest that in the Mexican setting, use of Truvada in place of standard Combivir and Kivexa for treatment of HIV is likely to be cost effective. These conclusions are supported by conservative assumptions and sensitivity analyses.