The randomized clinical trial is the highest level of evidence available for evaluating new therapies. However, serious deficiencies in study design and data analysis have been reported in reviews of clinical trials in medical and surgical journals. These deficiencies in study design introduce an element of bias into the trial results, which may lead to exaggerated treatment effects. To address these deficiencies in study design and preclude misleading results, criteria for excellence in randomized clinical trials have been published. Despite these publications, the quality of clinical trials in virtually all contexts that have been assessed has not improved substantively. With the ever-increasing dependency of new interventions in anaesthesia on evidencedbased outcome trials, it is hypothesized that the quality of trials in the anaesthesia literature has improved in the past 20 years.