In European health care systems one can notice an increase effort to base decisions on the outcomes of empirical studies, particularly in respect with their effectiveness and cost-effectiveness. Instead of the so-called ' opinion-based ' decision-making, health care policy and clinical practice should become more 'evidence based' by the introduction of guidelines based on scientific studies. Evidence based medicine (EBM) is seen as an important means to improve the quality of medical care as well as to control costs and to allocate resources. Though EBM is often seen as a rational and neutral process, ethical values and assumptions (e.g. on the goals of treatment) play a hidden but decisive role. By organising 5 workshops, the project wants to gather information on the ethical issues that are involved in the efforts to rationalise medicine and health care on the basis of empirical evidence. By an identification of the values and assumptions and making them explicit, these values can be subjected to professional and public debate. This debate will be stimulated by reports, academic publication, a bibliography, a set of recommendations and expert meetings.