In Brazil, the mandatory coverage of medical assistance by HMOs are reviewed every two years by the regulatory agency of the government. The incorporation of new technologies brings as a consequence the concern about rising costs. Most HMOs in Brazil does not have sufficient structure for conducting studies to evaluate adequately the impact on its budget. OBJECTIVES: Evaluate the economic impact of expansion of coverage through an economic health model that allows to simulate the results of any HMOs.  METHODS: We developed a decision support tool that automates the analysis of economic impact of new coverage according to the profile of the HMOs. The default rates used were based on the annual incidence of diseases and their prevalence according to sex, age, and history of use of procedures in the population. The costs of events considered the tariffs applied by HMOs and benchmarked prices commonly used. Adjustment coefficients were developed based on indicators of the real world in order to better reflect the market. As a basic principle, we followed the guidelines of the International Society of Pharmacoeconomics and Outcomes Research - ISPOR regarding the best practices.  RESULTS: The total addition in the medical and hospital expenses resulting from the incorporation of technology was of $ 2.02 per capita per month (plus 1.97%). The relative impact of major procedures was of $ 1.02 for immunobiological therapy (0.99%), $ 0.70 for eye treatment with antiangiogenic chemotherapy (0.68%) and $ 0.30 for the other corporate events (0.29%). CONCLUSIONS: The use of tools based on economic models enables to simulate variations in utilization rates, access to the use of procedures and costs, reducing the uncertainty of some health indicators. This makes it possible to predict scenarios that better represent the incorporation of technologies in the Brazilian private HMOs’ market.