The possibility of a single currency for the Mercosur countries was raised by Argentine President Menem in December 1997 and again at the regional summit this past June. This paper argues that whether Mercosur needs a common currency depends on what kind of integrated regional market its architects are creating. A customs union can be sustained despite the existence of separate national currencies that fluctuate against one another. But deeper integration extending beyond the border implies even more open domestic markets and more intense cross-border competition, making exchange-rate changes more disruptive. If South American policy makers intend to press ahead to deeper integration, then they like their European counterparts may have to contemplate monetary integration.
