This chapter reviews evidence-based medicine (EBM) from an historical viewpoint, together with an understanding of why it has developed. EBM offers a mechanism by which the available expenditure could be better distributed by clinical belief. It is therefore an idea of its age and has been readily accepted. The development of the EBM model for the management of medical care has paralleled the development of clinical trials. However, it is only since clinical trial methods have been established that EBM approaches have become applicable. The introduction of good clinical practice guidelines in the 1980s further strengthened the position of clinical trials in drug development. Despite the development of rigorous clinical trial methods, it became apparent that there is a gap between the results of randomized, blinded clinical studies and the practical use of the treatments in the usual clinical setting.