Purpose The purchasing of services is a significantly under-researched area. The purpose of this study is to suggest a conceptual model of service sourcing relationships, including the post-contract phase. Design/methodology/approach A qualitative methodology involving two longitudinal case studies that were analyzed with a grounded theory approach in order to build a conceptual model. Findings The proposed model consists of a core process that is termed ?business streamlining? and denotes the process by which four interrelated dimensions are managed in order to making the business processes of the buying organization simpler and more effective and/or productive. Research limitations/implications Although the research methodology is qualitative and does not allow statistical generalization, the study does provide valuable insights into the management of the service (out-) sourcing process. Practical implications The model proposed in this study can be utilized by managers to impose a useful conceptual structure on otherwise fluid and intangible processes, which makes them easier to analyze and facilitates strategic corporate decision-making. Originality/value The paper proposes a model that grasps the dynamics and reality of service (out-) sourcing relationships, including the ongoing relationship management process.