The way of interaction dominant on GATT and the World Trade Organization on one hand, and regionalism within the preferred groupings on the other, are among the important and sophisticated facts in international trade. While multilateralism puts the emphasis on non-discrimination (based on national acts and Most Favored Nation Clause) in international trade, regionalism is inclined towards preferred behaviors. However, both have grown up in parallel and governments are applying both. Specially, as during the recent decades and after the Uruguay Round lots of agreements have been concluded multilaterally and the WTO has replaced GATT, we witnessed a new wave of regionalism. However, in spite of incompatibility between these two approaches, the "openness" clause can make regionalism compatible with, and even complementary to the multilateralism. The APEC is a model close to the open regionalism which by some completing steps can be an appropriate pattern in this way.