The goal of this paper is to explore an applied tool for sensitivity analysis in computable general equilibrium models (CGE). An interregional CGE model is used to assess the impacts of the Free Trade Area of the Americas (FTAA) on Brazilian regions. As interregional substitution and factor mobility can be the key mechanisms that drive the model results, one should take closer attention to the estimated regional trade elasticities. Since information for proper estimation is rarely available, qualitative sensitivity analysis should be designed and used together with systematic quantitative sensitivity analysis. The sensitivity of results to parameters is evaluated in such a way that we can assess the robustness of results to different levels of elasticities of substitutionThe goal of this paper is to explore an applied tool for sensitivity analysis in computable general equilibrium models (CGE). An interregional CGE model is used to assess the impacts of the Free Trade Area of the Americas (FTAA) on Brazilian regions. As interregional substitution and factor mobility can be the key mechanisms that drive the model results, one should take closer attention to the estimated regional trade elasticities. Since information for proper estimation is rarely available, qualitative sensitivity analysis should be designed and used together with systematic quantitative sensitivity analysis. The sensitivity of results to parameters is evaluated in such a way that we can assess the robustness of results to different levels of elasticities of substitution