Clinical practice is complex and is influenced by a number of factors such as time since medical qualification, opportunities for further education and peer review, as well as trial results and marketing. Systematic audit and peer review are powerful tools that are being used increasingly. When aided by the intelligent, but not Draconian, use of financial carrots they are an effective means of changing practice. Positive trials, such as those of thrombolytic therapy, have rapidly resulted in the widespread use of such treatment. Negative trials, for example those involving anti-arrhythmic prophylaxis after myocardial infarction or the use of calcium antagonists in patients with impaired left ventricular function, have also correctly resulted in an appropriate change in practice. Advertising does not always reflect best clinical practice and could lead to under-promotion of older but more useful drugs. Peer review and audit are probably the best available methods for promoting good clinical practice.