Interorganizational systems (IOS) have become a required business practice for many companies with the partner relationship being an important factor in the effectiveness of the IOS. Theestablishment of trust between the partners of an IOS is often mentioned, yet, never examined when IOS research is reported. Using organizational theory as a foundation, this paper takes a macro approach in exploring the nature of the various IOS roles and discusses the significance of uncertainty, trust and communication on these roles. A model of the relationships between IOS role, uncertainty, trust and the choice of communication media is proposed.