This thesis provides a conceptual framework of power in buyer-seller relationships. Power as the potential to influence (or resist) the actions of others is an integral part of social reality yet its conceptual development is limited in the inter-organisational literature, which is dominated by descriptive empirical studies. Gaps in the extant literature relate to; what constitutes power in buyer-seller relationships, its underpinning ontological position, what buyers and sellers seek to influence and what motivates them to use their power. To enable the complex nature of power to be empirically captured and to reduce ontological constraints, a mixed-method research design was used incorporating three phases. The first two phases were exploratory to allow the practitioner population to identify variables associated with the research questions. Based on these outputs a questionnaire was designed and used as the primary data collection method. Through factor analysis, the results provide evidence that power is pluralistic and composed of multiple embedded realities. Power is held by individuals, organisations and relationships. The conceptual framework of power developed in this research underlines the importance of separating the various elements of power. Despite identifying some differences in attitudes between buyers and sellers, the results demonstrate considerable consistency of opinion between roles. Through this research, contributions are made to the conceptual development of power in buyerseller relationships.