There have been numerous studies about business-to-business (B2B) electronic commerce and market structure, most of them analyzing the relationships between buyers and sellers and the role of intermediaries. This research is based mainly on earlier papers about the role of information technology (IT) and electronic communications networks in the companies’ relationships. The use of these computerized inter-organizational networks leads to lower transaction costs, which encourages the development of electronic markets, where there is a severe price competition and greater buyer choice. In this chapter, we analyze the development of global B2B electronic markets and if these markets are becoming a way of improving trust between organizations at an international level, increasing, therefore, the inter-organizational cooperation among them. Based on the literature review and on the analysis of some global electronic markets, we define and describe these platforms, stressing the strategic role of each of the principal participating actors. Furthermore, we propose a model to explain the trust-related sources of competitive advantage for the new intermediaries in electronic markets and compare those with the off-line market’s characteristics. In addition, some propositions related with the trust-building mechanisms are defined.