This chapter reviews the effects of cost-effectiveness based medical decision-making (CEM). Reviews of the effects of CEM have also – like in evidence-based medicine – pointed to the time constraints imposed by it on retrieving information. In addition, these reviews also point to other problems in the use of cost-effectiveness information in medical care. Medical care is very diverse, in terms of its remit, technology, and its purpose and control. Each of these diversities causes a difficulty in the application of CEM. CEM makes an assumption that the purpose of health care structures is to provide efficient health care. In many ways the development of purchaser—provider relationships is the reason why there is such a demand for CEM. Purchaser-provider splits – also called internal or quasi-markets – are an attempt to harness the power of economics into medical decision-making.