Limited resources in the health sector force a process of choice between alternative health care programs and services and patients or groups of patients who will receive care. In the absence of a price mechanism, the priority-setting process serves to allocate scarce resources among competing uses, and is thus a form of rationing. Traditionally, implicit approaches have dominated the health sector's decision-making, mostly by physicians. However, in the face of increasing budget constraints and rising patient expectations, more explicit and socially acceptable priority-setting practices are needed. Internationally, the development of explicit prioritization has proven difficult and controversial.