Research on interorganizational partnerships (IOPs) points to high levels of information-sharing, mediated by interorganizational systems (IOS), as a determinant of value creation. However, it is widely acknowledged that such interactions are characterized by opportunism, leading to transaction costs. Interfirm trust has been posited as one mechanism for reducing transaction costs and promoting rich information sharing. In this research-in-progress, we seek to understand the role of trust in facilitating information sharing in one form of IOS—electronic market access forums (EMAFs). We draw on transaction cost economics (TCE) to suggest that the dominant trust-based mechanism in an EMAF exchange is contingent upon the nature of information exchanged. This study will enhance understanding of how different types of trust influence information sharing in IOPs, and, potentially, offer guidelines on how EMAF providers can improve their margins by fostering different forms of trust-based governance.