This article presents a model of real exchange rate using a neokeynesian approach, which is estimated with econometric methods of the English school. The empirical model is dynamic and respects the restrictions of the long run equilibrium between real exchange rate and macroeconomic fundamentals. It shows that the amount of appreciation and depreciation of the real exchange rate is determined by changes in terms of trade, openness of the economy, capital flows and acceleration of nominal devaluation. Public spending increases are not significant of the conventional levels of statistic confidence. Finally, the article evaluates if devaluation meets the requirements of weak, strong and super exogenity.