Using detailed plant-level manufacturing Census data from the Colombian Agri-food industries, we show that exports raise plant-level productivity by about 15 to 20 percent. However, the estimates reveal that efficiency in plants that become persistent exporters, i.e. plants that service foreign markets at least 30 percent of the time during our sample years 1981-1991, increases about 30 percent upon their entry into foreign markets, while productivity in plants that become only occasional exporters does not change at all. Hence, the positive impact of exports on productivity for is driven by the large positive impact on persistent exporters. To identify the effect of exports on plant-level productivity we employ the Levinsohn-Petrin (2003) measure of total factor productivity and a difference-in-differences propensity score matching estimator. The estimates reveal that productivity in plants that become persistent exporters, i.e. plants that service foreign markets at least 30 percent of the time during our sample years 1981-1991, rises about 30 percent upon their entry into foreign markets. Productivity in plants that become only occasional exporters, on the other hand, does not change. We perform a number of robustness checks, all of which confirm our baseline results.