Many studies have been done concerning the impact of the General Agreement on Tariffs and Trade (GATT) on economic activities such as production, consumptions trade, and prices. This study examines whether GATT reforms improved market integration and efficiency using the beef and wheat markets as specific cases. Whereas earlier studies specified general or partial equilibrium structure in their models, this study uses time series methods with minimum structural specification. The author suggests there is consistent evidence that GATT reforms promoted market integration and improved market efficiency.