The latest medical buzz phrase is evidence based. This term has become a shibboleth, a sacrosanct icon almost like motherhood. Who could possibly be against basing decisions on evidence? It is difficult to think of a polite term for decisions not based on evidence. The almost religious zeal for cloaking all decisions under the banner of evidence basedconceals the real problem—that is, what is the evidence? Does it apply to the individual patient being treated? What is the context in which the evidence was gathered and it will be applied?

When historians look back on the last quarter of the 20th century, they will emphasise four developments: (1) dramatic improvement in diagnostic technology, especially brain related, (2) major advances in genetics and molecular biology, (3) computer facilitation of data bases and reference resources, and (4) focus on treatment and therapeutic trials. Greater interest in treatment is a natural consequence of improved diagnostic capabilities. Although therapeutic trials were conducted in the 1950s, during the past two decades the methodology and the statistical planning and analysis of trials have developed a more sound scientific basis.

Recently, there has been a determined effort to integrate results of therapeutic trials into medical care. This integration is the strongest type of “evidence base.” Delivery of therapeutic data from randomised trials, on line, to practising physicians has only recently become a reality. Doctors now have rapid access to diagnostic and therapeutic data bases using portable or office based computers. This capability brings scientific medicine into doctors' offices, and hospitals quickly and cheaply.

Marriage of the therapeutic and computer eras has led to the proposition that treatment should be based on data from therapeutic trials. Treatment based on trials is naturally preferred over treatment not based on trials. Most treatment reviews now contain wording that …