This paper is about what role the Most Favored Nation(MFN) principle plays in international trade relations under the current WTO system. It is one of the most basic principles in international trade and has a long history tracing back to the twelfth century. This principle, causing the utmost favors given to one country to spread to other countries, promotes trade liberalization and helps countries to eliminate discrimination and guarantee equal status among countries. GATT has made great contribution in eliminating discrimination in international trade and liberalizing it by specifying in the number one clause that every member country is obliged to treat other member countries as the most favored nations. Under the WTO system, this principle holds the place of the most important principle in GATS and TRIPS as well as in GATT. It is investigated, by examining each clause in the WTO agreement, in what area, in contemporary international trade, the principle is respected and in what area it is not. The current international trade relations allow too many exceptions deviating from the MFN principle while they assume it as the basic principle. Moreover, regional economic integration, preference to developing countries, and bilateralism, among others, reduce the areas of its application. The MFN principle should be observed more strictly and applied to more areas of international trade for stable development of international economics.