This paper argues that the use of subnational data allows an accurate assessment of the effect of trade agreements on bilateral exports within a gravity model framework. We examine the effect of regional integration on trade flows from regions in Argentina, Brazil, Poland and Spain to a sample of importing countries. Specifically, we focus on two events that occurred in the EU and in Latin America over a decade ago: the EU enlargement to the Central and Eastern European countries, and the signing of a Free Trade Agreement between two Latin American regional blocs, the Southern Common Market and the Andean Community.