Large movements in exchange rates have small e ffects on the prices of internationally traded goods. Using a new dataset on currency invoicing of Belgian fi rms, we study how the currency of invoicing interacts with fi rm characteristics in shaping the extent of exchange rate pass-through at di fferent time horizons. The US dollar and the Euro are the dominant currencies in both Belgium’s exports and imports, with substantial variation in currency choice across fi rms and products even within narrowly de fined manufacturing industries. We fi nd that smaller, nonimport-intensive fi rms tend to denominate their exports in euros and exhibit nearly complete exchange-rate pass-through into destination currency prices at all horizons. In contrast, the largest most import-intensive firms, and in particular with imports denominated in US dollars, tend to also denominate their exports in US dollars and exhibit much lower exchange rate pass-through at all horizons. We show that these empirical patterns are in line with the predictions of a theoretical framework featuring heterogeneous fi rms with variable markups, endogenous international input sourcing and staggered price setting with endogenous currency choice. We plan to use a variant of a such model, disciplined with the Belgian firm-level data, for counterfactual analysis of the gradual increase in the use of the euro in international trade fl ows.