This paper studies the firm-level relationship between decision to export and environmental performance. To guide the empirical work, we introduce environmental pollution and technology choice into a trade model with heterogeneous firms. The model predicts that a productive firm is more likely to adopt emission-saving technology and to export. Using facility-level criteria air emission data in the U.S. manufacturing industry, for a variety of pollutants, empirical tests are supportive of our two primary theoretical predictions. First, facility productivity is negatively correlated with emission intensity, measured by emissions per value of sales. Second, conditional on the estimated facility productivity and the facility's exposure to environmental regulation, exporters have lower emission per value of sales than non-exporters within the same industry.