A gravity model is used to asses the separate effects of exchange rate volatility and currency unions on international trade. The panel data set I use includes bilateral observations for five years spanning 1970 through 1990 for 186 countries. In this data set, there are over one hundred pairings and three hundred observations, in which both countries use the same currency. I find a large positive effect of a currency union on international trade, and a small negaitve effect of exchange rate volatility, even after controlling for a host of features, including the endogenous nature of the exchange rate regime. These effects are statistically significant and imply that two countries that share the same currency trade three times as much as th...