Article dans une revue: We use data on individual French exporters to document how a change in trade costs following the introduction of the euro affected firms' export margins in relation to export decisions, the number of products exported and average sales per product. Our results confirm two effects predicted by the theory: firms increase the range of products they export as well as their intensive margin. This effect is most evident in markets with moderate monetary policy coordination before 1999. General equilibrium competition effects reduce the initial positive impact on each of these margins. We find no evidence of firms' increased export participation