The General Agreement on Trade and Tariffs aims at liberalizing trade between countries in order to realize additional gains to the international economy and world nations' welfare. This agreement represents challenges and in the same time opportunities and advantages from which countries can benefit and try to maximize their potential gains from GATT. The study has depended on Chow Test to show the effects of GATT on the economic variables related with foreign trade and its efficiency. The results has shown that there was a significant effect on GDP, total exports, total imports, agricultural exports, agricultural imports and imports from food commodities during the two periods of study, where it has shown that GDP has a significant increase before and after the establishment of GATT. This increase amounted to about 17.59% and 6.91% for the two periods respectively. The total exports has a significant increase in the first period, 15.66% from the average. In the second period the significant increase amounted to about 19.11% from the average. The total imports has a significant increase in the two periods of study, the rate of increase in the first period amounted to about 12.44% from the average, whereas it has amounted to about 8.6% in the second period. According to the agricultural exports, it has a better situation in the second period, where it has a significant increase amounted to about 20.36% from the average in that period. The agricultural imports had insignificant increase before the implementation of the GATT, where it has a significant increase after GATT that amounted to about 12.34% from the average. According to the imports from food commodities, it has a significant increase before the GATT, where it has a significant decrease in the second period that amounted to about 14.51% from the average, and this represents the increasing of food agricultural production. According to the effects of GATT on the foreign trade efficiency it has shown that total export and agricultural exports efficiency has increased through the increase of average rate of total exports by 2.7%, and the increase of average rate of agricultural exports by 5.55% in the second period. Also for the total imports or agricultural imports, they have improved where the average rate of imports has decreased by 9.2% and the average rate of agricultural imports has decreased also by 2.43%. According to the coverage rate of exports to imports we can see that the total coverage rate has increased by 4.97% and the agricultural coverage rate has increased by 4.81% in the second period. According to the market access rates, it has shown that the movement of foreign trade was in favor to the total exports to the foreign markets during the two periods. But fore the agricultural market access, the imports has decreased in the first period but increased in the second period.