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The culture of evidence-based medicine dictates that clinical decisions are made in the light of the best available evidence. In ascending order of validity, that evidence maybe found in the form of case reports, expert consensus opinions, laboratory experiments, randomised clinical trials (RCTs) or meta-analyses. In broad terms, case reports supply inadequate information on which to base decisions that may influence a large and varying population. Consensus opinions offer experience-based guidelines, but usually with the caveat that evidence is lacking on specifics. Laboratory experiments address those specifics, but suffer from the criticism of being remote from the clinical environment. The theory of design and method of the RCT, the building block of meta-analysis, are accessible to most. Thus, examples may be found for a wide spectrum of clinical situations, and so it is this level of evidence upon which many clinical decisions are based. Meta-analysis occupies the scientific high ground, but requires that comparable quality data are available from multiple RCTs, and controversy persists as to whether they amplify rather than reduce the problems experienced with RCTs.