For many organisations e-Procurement has become a necessity. Nevertheless, while e-procurement has generated considerable hype the phenomenon is generally under-researched. This paper explores the effects that business-to-business relationships have on e-Procurement systems using a field study of 6 companies. The study classifies business-to-business (B2B) relationships as being adversarial and collaborative, and examines the effects that each have on the electronically supported transaction phases of the procurement lifecycle. The research findings indicate that B2B relationships have most effect on the sourcing, fulfilment, and consumption phases of the procurement cycle