This paper explores how purchasing contributes to the management of supplier relationships (SRs) and how certain characteristics of the products/services that are exchanged can influence this contribution. There is a widespread awareness that purchasing has an important role in the management of SRs, yet there is an incoherent view of the activities that it actually contributes to the management of SRs and how this contribution is mediated by the nature of products/services that are exchanged. A large survey is conducted to identify the activities of purchasing involvement in SRs' management. Case studies are also conducted by examining diverse SRs that involve the exchange of products/services with different levels of asset specificity and criticality to identify their mediating role. The paper contributes to the current discussion of the role of purchasing in supply chain management and develops an analytical framework of the activities that purchasing managers conduct in SRs in terms of product management, process management, contract management and supplier development, and shows that for products/services with high levels of asset specificity and criticality its contribution is limited.
