This paper examines the effects of information technology (IT) on the governance of vertically related firms. We propose that a highly relation-specific IT system in inter-firm transactions plays a key role in the resulting inter-firm governance as a mutual sunk-cost commitment, in terms of leading to both less vertical integration (i.e., a change in governance mode as a first-order effect) and a smaller number of suppliers (i.e., a change within a governance mode as a second-order effect). As a result, this highly relation-specific IT system (bilateral investment) can be an alternative governance mode of electronic integration that acts as a substitute for managerial hierarchy and vertical financial ownership. From a strategic management perspective, this paper provides transaction costs and resource-based explanations on IT systems' impact on the organizational boundary decision and its impact on the likelihood of the firm achieving sustainable competitive advantage. Copyright © 2006 John Wiley & Sons, Ltd.