This chapter model the factors behind the instability of exchange rate by using exchange market pressure (EMP) index. The authors focus first to construct the EMP and then secondly, test the interrelationship between EMP, real gross domestic product, money supply (M2), consumer price index, trade openness and share price using quarterly data in selected East Asian countries. The empirical results of this study explicitly indicate that EMP is determined by the states of other variables in most of the studied countries. Planning on the macrolevel is essential when managing and ensuring continuous monitoring of the exchange rate condition. This would translate into positive macroeconomic welfare and economic growth sustainability.