Abstract This paper assesses the empirical desirability of the East Asian economies to an alternative exchange rate arrangement (a monetary union) that can potentially enhance the exchange rate stability and credibility in the region. Specifically, the symmetry in macroeconomic disturbances of the East Asian economies is examined as satisfying one of the preconditions for forming an Optimum Currency Area (OCA). We extend the existing literature by improving the methodology of assessing the symmetry shocks in evaluating the suitability of a common currency area in the East Asian economies employing the Bayesian State-Space Based approach. We consider a model of an economy in which the output is influenced by global, regional and country-specific shocks. The importance of a common regional shock would provide a case for a regional common currency. This model allows us to examine regional and country-specific cycles simultaneously with the world business cycle. The importance of the shocks decomposition is that studying a subset of countries can lead one to believe that observed co-movement is particular to that subset of countries when it in fact is common to a much larger group of countries. In addition, the understanding of the sources of international economic fluctuations is important for making policy decisions. The falling share of country specific factor and the rising role of region factor indicate that East Asia has become increasingly favorable for a monetary union. However, the share of country-specific factor that is still significant implies that it could be costly to renounce individual currencies to advance into a monetary union in East Asia.