Based on the reconstruction of the monetary flows of a merchant-banking company operating in Barcelona at the beginning of the fifteenth century, this study aims to understand the reasons behind exchange-rate variations in the local currency with respect to the principal European markets, as well as the modalities and predictability of such oscillations. By using real rather than ‘hearsay’ rates, we present new assessments of the seasonal character of exchange rates and their sensitivity to conditions of currency abundance or shortage. In addition, econometric analysis shows that exchange-rate volatility was quite modest and dependent on geographic and macroeconomic factors, such as the system of commercial flows.