Evidence-based medicine was one of the earliest manifestations of evidence-based policy and practice, and has exercised substantial influence on other policy areas. Based on data from seven empirical studies carried out between 1993 and 1999, this article examines the origins and impact of EBM, and the complexities of implementation which have emerged. Policy makers and EBM enthusiasts alike have frequently taken a somewhat simplistic view of the implementation gap they seek to address. Understanding clinicians' mixed reactions to the rhetoric of EBM helps explain both why EBM has had as much impact as it has, and why it has sometimes been resisted and rejected. Although other areas of public policy can learn from the experience of EBM, there are distinctive features of health care which set it apart, notably the continued autonomy and dominance of the medical profession and the strong influence of the biomedical science model on what is considered legitimate evidence.