Abstract Developing buyer–supplier relationships has been relatively ignored in the literature. This paper proposes a practical approach to evaluate and plan improvements in a supply relation, consisting of two parts. Firstly, a supply chain concept is proposed that consists of four areas: physical supply, planning and control, organisation and relation, and flow of information. This concept is useful in describing and analysing a supply relation. Secondly, a method based on scenario planning is used to generate alternative designs of a supply relation and to stimulate discussion. The approach is applied for a hospital and its supplier of gasses. The application helped considerably in gaining knowledge about the actual working of the supply relation of both organisations. The alternative scenarios stimulate discussion and development of their relation. The paper also contributes to the knowledge of applying supply chain management concepts in a hospital.