Inter-organisational systems (IOS) are of great importance to businesses as these systems enable different organisations to work together through the exchange of information. Despite this significance, the diffusion of IOS is disappointingly slow. There have been a number of studies of the factors affecting IOS adoption but they have yielded inconsistent results. We argue that adoption of IOS is also contingent upon the motivations of organisations. In this paper, we develop a model that explains the variation in motivations for IOS adoption. The model categorises motivation to adopt IOS along two dimensions; type of motivation and locus of motivation. The model also provides four scenarios for IOS adoption and identifies typical tasks for each scenario. The model can help practitioners and researchers to better understand the differences in motivations between particular organisations involved in IOS implementations.