This paper focuses on trust in the adoption of newly emerged interorganizational systems (IOS) -Radio Frequency Identification (RFID) systems-in contractual alliances. Much of the prior research on IOS adoption has concentrated on relationships where one of firms, such as Wal-Mart, has had considerably more power and influence than others. This paper examines alliances where member firms have balanced power and where full cooperation of all related members is required to achieve the full benefits of technology implementation. We propose that different social categories within an alliance, especially categories formed by the differential use of RFID, play an important role in shaping group members' perceptions and beliefs about RFID systems as well as about each other, and their decisions about adopting the systems. The paper enhances our understanding of IOS adoption by incorporating into the analysis the characteristics of the group of organizations making up the alliance.