U.S. imports of fresh fruits and vegetables have increased sharply since the late 1980's. With increased imports come increased concerns that pests and diseases may infest shipments of fresh agricultural products. To address this concern, USDA's APHIS implements phytosanitary measures that mitigate pest and disease risks. These regulations vary from documentation requirements, inspection, or requiring that shipments receive a phytosanitary treatment. A growing body of literature attempts to assess the generic trade flow effects of SPS measures. Still, little evidence is available to shed light on the nature, size, and scope of SPS standards and their role as "trade barriers" versus "trade catalysts." This thesis fills the void in the literature in two respects. First, a novel database on phytosanitary measures pertaining to U.S. imports of 47 fresh fruit and vegetable products from 95 countries is developed for the period 1996-2007. This disaggregated approach allows for the effects of specific phytosanitary treatments to be identified. Second, following recent literature, the issue of "zeros" is addressed while estimating a gravity model of international trade. The findings suggest that phytosanitary treatments initially inhibit fresh fruit and vegetable imports. However, their trade reducing effects are uneven across product sectors, development status categories and treatment types. Finally, globally large exporters facing a treatment requirement ship more fresh fruits and vegetable relative to small exporters facing the same regulation, suggesting the role of SPS measures as "trade barriers" versus "trade catalysts" depends on the relative size of the exporter in the global market.