In the literature on interorganizational systems (IOS) one encounters mainly examples of information systems that support highly structured transactions between organizations. However, the range of interorganizational activities also includes less structured interactions, such as negotiations and joint problem solving. This paper wants to contribute to a better understanding of the potential of IOS by developing the notion of a high-level IOS. Technological and managerial challenges are delineated that have to be mastered in order to reach high-level IOS. Underlying the analysis of these challenges is the prediction of an evolution of IOS that is based on the analysis of the evolution of internal information systems (IS).