A critical feature of the reforms to the National Health Service (NHS) in the United Kingdom is the separation of responsibility for purchasing and providing health care. In the new structure, health authorities purchase care from a population perspective, and general practitioner fundholders undertake patient-focused purchasing. The evidence suggests that each approach has distinctive advantages. There is, however, a risk of fragmentation if the decisions of the different types of purchaser are not coordinated. This risk is compounded by the emergence of hybrid models combining aspects of population-centered and patient-focused purchasing. The separation of purchasing from providing has changed the balance of power within the NHS, although whether the benefits of the new system outweigh the costs is a matter of continuing debate.