Until now, most of studies on Electronic Data Interchange(EDI) have been focused on the introduction of EDI and the performance of EDI. But recently, there have been increasing researches on diffusion of Electronic Data Interchange. The aims of this study are twofold. First, to find the impacts of various factors on EDI diffusion, second, to examine the relationship between EDI diffusion factors and EDI diffusion degree. To accomplish those aims of study, two kinds of methodologies are adopted in the studies, First, model building by wide investigation on previous papers, Second, empirical research for finding the determinants of diffusion of EDI. The results of testing the hypotheses of this research are summarized as follows. First, The important EDI diffusion variables influencing internal diffusion of EDI consist of top management support, scope for EDI, IS sophistication, compatibility, complexity, relative advantages, competition intensity and external pressure. Second, Top management support, scope for EDI, IS sophistication, compatibility, relative advantages, competition intensity and external pressure are associated with external diffusion of EDI. We are aware of the important fact that top management support, scope for EDI, IS sophistication, compatibility, relative advantage, competition intensity and external pressure were simultaneously associated with internal and external diffusion of EDI.