This paper studies the impact of monetary arrangements on trade integration and business cycle correlation in late 19th century Europe. We estimate a gravity model and show that tighter monetary integration was associated with substantially higher trade, as in recent studies using contemporary data. For instance, the Austro-Hungarian monetary union improved trade between member states by a factor of 3. To explain this, we build and estimate a simple model where greater monetary integration weakens the current account constraint by fostering business cycle co-movements. Copyright Springer Science + Business Media, Inc. 2005optimum currency areas, endogeneity, trade, business cycles, monetary union,