Using transactions-level customs data from Colombia, we study firm-specific exporting patterns over the period 1996-2005. Our data allow us to track firms’ entry and exit into and out of individual destination markets, as well their revenues from selling there. Our results support findings from previous work: Exporters are very heterogeneous in terms of their size and the number of destinations where they sell. Since previous studies have not been able to use data on firms entering and leaving individual export markets, they have been unable to study patterns of entry and exit. The panel data in the current study provide information on how exports by individual firms to specific destinations evolve over time. While many firms enter and exit from exporting, these firms tend to be small in terms of their overall contribution to export revenues. Export sales are dominated by a small number of very large and stable exporters. In terms of the life cycle of exporting firms, most entering firms leave after one year of exporting. A small minoriTY go on to become stable incumbents.