In recent years， the number of preferential trade agreements（PTAs）increases rapidly． In tandem with the evolution of the new trade theory， the economic ana豆ysis of PTAs has also been developed drastically． This paper intends to organize a complicated mass of existing theories of PTAs and places special emphasis on their relationship with multilateral trade liberalization． Some new topics such as the effects of intemal market integration or those of rules of origin are also discussed
