E-procurement systems, which represent a core e-supply chain initiative, are intended to revolutionaise the manual procurement function of organisations and promise many benefits. However, realisation of benefits from e-procurement systems implementation is not always guaranteed. Despite many of years of research into e-supply chain, there exists no theoretical model to help management predict the likely benefits that their organisations may experience from implementing an e-procurement system. In this paper, we propose a model for better explaining the benefits that an organisation may expect to experience from these systems. The model identifies four types of relationships which organisations may choose to establish with suppliers while deciding to introduce an e-procurement system, and associates each relationship type with a set of predicted benefits. We further present the e-procurement experience of a government agency, analyse it in terms of the model, and provide empirical support for the applicability of part of the model.