Before applying indtlstrial organization and marketing theory to interrigonal competition, it is necessary to be accurate about the concept of interrigonal competition, J.D. Black and R.L. Migliell have defined it as supply responce to price and comparative advantage of farm organization. Though interrigonal competition is founded upon the theory of location, especially resources mobility or immobility regulating supply reresponse in longrun, and farm organization adjustment in respect to region without recognized market structure, and farm organization adjustment in respect to region without recognized market structure, yet according to W.F. Williams, traditional agricultural marketing, that is, not only institutional, comodity and functional approach but also perfect competition theory which C.S. Shepherd and R.G. Bressler evolved a new theory (marketing efficiency) could not account for market structure change. Market structure research may be summarized as follows. 1. The theory of market structure has been developed by R.L. Clodius and Muellers applied inductrial organization theory, especially J.S. Bain made up the theory to the competition for buyer of agricultural products arter W.H. Nicholls had evolved price theory in relation to inperfect competition. 2. Fundaniental probiems of market structure research were discussed by W.F. Williams, J.R. Moore and F.T. Smith about that market performance was decided on both market conduct and market structure, and that structural change of market should be market conduct, namely, patterns of firm behavior, interact market structure. 3. If a dynamic approach of market structure is developed within the frame-work of industrial organization theory, variables and combination of variables of market structure and market conduct will depend on the industrial structure in spite of J.S. Bain's theory, as long as the concept of industry does not accord to the cocept of market.