The authors apply a Heckman selection model to the 2003 Investment Climate Survey (ICS) to investigate supply-side constraints to export performance at the firm level in Ecuador. To correct for the non-random truncation problems, they use the Heckman selection model to estimate the probability of exporting (export propensity) and the share of total sales that are exported (export intensity) by Ecuadorian firms. They develop a baseline model with 12 independent variables divided into three categories-idiosyncratic characteristics, technology, and business environment. The authors develop three other models with the addition of variables related to trade integration, business environment, and infrastructure. Results corroborate with the hypothesis implicit in the Heckman model, which considers both decisions made by a firm-whether to export, and how much of its sales to export-to be interdependent. In the Ecuadorian case, they find three important results for the firm's export performance: technology matters; infrastructure does not; and trade orientation is significant, with specialized firms tending to have smaller export intensity when their main trade partners are countries of the Andean Community, and the opposite happening if the United States is their main trade partner. The authors find a robust and stable relationship for export propensity and intensity with size, import of inputs, labor regulations, in-house research and development, quality certification, web-use, and foreign ownership. Also, capacity utilization and trade with the United States positively affect export intensity, while trade within the Andean Community has the opposite effect in the outcome variable. But they find no significant relationship for the infrastructure variables.