Business-to-business (B2B) marketplaces have significant potential impacts on the structure of channel relationships and IT management arrangements. IS theory traditionally investigated electronic marketplaces from a transaction cost theory point of view. We identify three major limitations of transaction cost theory as it applies to B2B electronic marketplaces. A number of other literatures with a bearing on electronic marketplaces have critiqued and extended transaction cost models. Among them are strategic networks theory, marketing channel theory, and political economy. This paper reviews and attempts to synthesize these perspectives on electronic marketplaces and exchanges. We propose an integrative model combining transaction cost theory, strategic networks theory, relational exchange theory, and the theory of political economy. The synthesis promotes better operationalizations of EMP channel structure, identifies the antecedents and consequences of EMP channel structures, and suggests an agenda for future research.