Health Care Analysis 7: 139–151, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. Priority Setting and Evidence Based Purchasing LUCY FRITH Department of Primary Care, University of Liverpool, Liverpool L69 39B, UK Abstract. The purpose of this paper is to consider the role that values play in priority setting through the use of EBP. It is important to be clear about the role of values at all levels of the decision making process. At one level, society as a whole has to make decisions about the kind of health provision that it wants. As is generally accepted, these priority setting questions cannot be answered by medical science alone but involve important judgements of value. However, as I hope to show values come into priority setting questions at another level, one not often explicitly recognised in much of the literature: that of the very definition of the effectiveness of treatments. This has important consequences for patient care. If we do not recognise that the effectiveness of a treatment involve subjective elements – a patient’s own assessment of the value of the treatment – then this could lead to the belief that we can purchase one treatment that is the most effective for all patients. This might result in a detrimental reduction in the range of options that a patient is given with some patients not receiving the treatment that is most effective for them. Key words: priority setting, evidence based purchasing, values, ethics, effectiveness Introduction In recent years evidence based purchasing (EBP) has become the predom- inant means by which health priorities are decided. This paper considers its role in prioritising which treatments the health service should provide. The central theme is an examination of what role values play in a process which is sometimes couched in the language of science and objectivity. By values I mean both ethical considerations – what is right or wrong – and also values, in terms of personal and/or institutional preferences. In discussions of EBP the medical literature does not often explicitly discuss the role values play. However, this lack of discussion does not mean that values themselves are absent from the decision making process. All the EBP literature sometimes contains explicit, but more often implicit, assump- tions about the role that values play, or don’t play, in the use of medical evidence. These assumptions can be usefully divided into three broad philo- sophical positions which I have called scientism, the mixed strategy, and the evaluative position.