Information technology (IT) has long been applied to support the exchange of goods, services and information between organizations. It is with the advent of Internet-based e-procurement systems and businessto-business (B2B) electronic markets that the real opportunities for online transactions have opened up across space and over time. In this paper, we draw on IS and economics theory to investigate the motivation for the various online business models, and the adoption requirements of purchasing firms, through the examination of a set of mini-cases. Our exploratory study finds that private aggregating and negotiating mechanisms are being adopted for large quantity business supply purchases, while public market mechanisms are more often adopted when firms face uncertain and high variance demand. Moreover, market facilitation, expertise sharing and collaboration are gradually attracting more attention, and call for future investigation.