The article aimed to draw some implications for regional exchange rate cooperation from the experiences of EMS. EMS, which used to be the exchange rate cooperation from 1979 to 1999, contributed to the stability of price and exchange rate. However, it revealed various limits that were not expected at the outset. The crisis of EMS was caused by several reasons; the fixed exchange rate system with narrow-band that was taken when the economic fundamentals of each country were not fully converged, the asymmetric distribution of the cost for exchange rate adjustment, and speculative attack on the currency market. In the end EMS had to enlarge exchange rate band of fixed exchange rate system with narrow-band. From these experiences of EMS we can draw some implications for regional exchange rate cooperation in East Asia: First, like ECU of EMS, the common currency basket composed of currencies of East Asian countries should be taken as key currency for the sake of stability of regional exchange rate. Second, exchange rate band should be enlarged so that we can change basic exchange rate without causing exchange speculation on the currency market. Third, the intramarginal intervention is desirable in order to keep stable exchange under the enlarged exchange rate band.