The Real Exchange Rate (RER) represents the nominal exchange rate adjusted by the relative price of domestic and foreign goods and services, thus reflecting the competitiveness of a country with respect to the rest of the world. More in detail, an appreciation of the currency or a higher level of domestic inflation drives up the RER, worsening the country’s competitiveness and reducing the Current Account (CA). On the other hand, a currency depreciation generates an opposite effect, improving the country’s CA.There is evidence that the RER generally reaches a steady level in the long-term, and that this process is faster in small open economies characterized by fixed exchange rates. Any substantial and persistent RER deviation from its long-run equilibrium level, the so-called RER misalignment, has shown to produce negative impacts on a country’s balance of payments. An overvalued RER means that the current RER is above its equilibrium value, whereas an undervalued RER indicates the contrary. Specifically, a prolonged RER overvaluation is widely considered as an early sign of an upcoming crisis, due to the fact that the country becomes vulnerable to both speculative attacks and currency crisis, as happened in Thailand during the 1997 Asian financial crisis. On the other side, a protracted RER undervaluation usually generates pressure on domestic prices, changing the consumers’ consumption incentives and, so, misallocating resources between tradable and non-tradable sectors.Given that RER misalignment and, in particular overvaluation, can undermine the country’s export-oriented development strategy, the equilibrium RER measurement is crucial for policymakers. Unfortunately, this variable cannot be observed. The most common method in order to estimate the equilibrium RER is the universally accepted Purchasing Power Parity (PPP) theory, according to which the RER equilibrium level is assumed to remain constant over time. Nevertheless, the equilibrium RER is not a fixed value as it follows the trend of key economic fundamentals, such as different monetary and fiscal policies or asymmetrical shocks between the home country and abroad. Consequently, the PPP doctrine has been largely debated during the years, given that it may signal a natural RER movement towards its new equilibrium as a RER misalignment.Starting from 1980s, in order to overcome the limitations of this approach, many researchers tried to find some alternative equilibrium RER measures. Two of the most popular approaches in the economic literature are the Fundamental Equilibrium Exchange Rate (FEER), developed by Williamson (1994), and the Behavioural Equilibrium Exchange Rate (BEER), initially estimated by Clark and MacDonald (1998). The FEER focuses on long-run determinants of the RER, rather than on short-term cyclical and speculative forces. It represents a RER consistent with macroeconomic balance, characterized by the achievement of internal and external balances at the same time. Internal balance is reached when the level of output is in line with both full employment of all available factors of production, and a low and stable rate of inflation. On the other hand, external balance holds when actual and future CA balances are compatible with long-term sustainable net capital flows. Nevertheless, the FEER is viewed as a normative measure of the RER since it is based on some “ideal” economic conditions related to internal and external balances. Particularly, since the sustainable CA position is defined as an exogenous value, this approach has been broadly questioned over time. By contrast, the BEER entails an econometric analysis of the RER behaviour, considering significant RER deviations from its PPP equilibrium level as a consequence of changes in key economic fundamentals. According to this method, the BEER is the RER that results when all the economic fundamentals are at their equilibrium values. Therefore, the total RER misalignment is given by the extent to which economic fundamentals differ from their long-run sustainable levels. In short, the BEER is a more general approach than the FEER, since it is not limited to the long-term perspective, being able to explain RER cyclical movements.