In response to a growing interest in key supplier management (KSM) among business practitioners and academics, this study aims to identify the conceptual locus and the functionality of KSMwith reference to the components of a business relationship. A multi-dyadic case study was carried out focusing on KSM in relationships between a multinational electricity-distribution company and its nine key suppliers. The KSM system turned out to be a component of the technical setting of the relationship structuring the interaction, but also more widely guided the joint developmental means for improving value creation. It acts as a channel through which the buyer's and the supplier's goals are implemented in building an infrastructure for effective performance within and outside the key supplier relationship. Further qualitative research would enhance understanding of KSM in its organizational and inter-organizational contexts in terms of defining constructs and their interrelations to be tested in quantitative research