The papers in this section are all based on talks given at a conference last October to mark 50 years of clinical trials, organised by the BMJ and the Medical Research Council

Identifying the efficacy of treatments from the data from randomised controlled trials is the first step in improving the efficiency of medical care. The implementation of clinical practice guidelines on the basis of this evidence, and prioritising of practice on the basis of cost effectiveness studies, are the next steps. Psychiatry seems nervous about trusting itself to this process. It is 50 years since the first randomised controlled trial in medicine, and doctors in other specialties seem sufficiently comfortable with the method to form research practice consortia and to conduct mega-trials 1 2 that are comparatively immune to the methodological and political hazards that can beset small randomised controlled trials and meta-analyses 3 4 Why, then, have mega-trials not begun in psychiatry? There are two important reasons: the types of treatment used, and the nature of the endpoints. Psychological treatments can be effective and, in certain disorders, more effective than drugs.5 It is easy to be certain about the quality of drugs, but psychological treatments, unless manualised for both physician and patient, depend on the fidelity with which practitioners carry out the treatment Next, the 22% of the global burden of disease attributed to mental disorders is made up of 21% from morbidity and only 1% from mortality.6 Measuring morbidity or disability is much more complex than measuring mortality, the usual endpoint in mega-trials of physical disorders