Much of the practice of cardiothoracic anaesthesia and critical care developed without an evidence base. However, in recent years there have been an increasing number of randomised controlled trials (RCTs). In some areas their findings have been inconclusive often because their sample size has been too small. Where there are a sufficient number of such studies, some areas of research have been subjected to meta-analysis. Some of these have been inconclusive because of a lack of good quality studies upon which to base them. Others, such as atrial fibrillation (AF) prophylaxis, have clearly identified efficacious therapy yet they have been found to have no influence on important clinical outcomes. Remarkably, there are yet others that have been ignored whilst researchers continue to undertake trials to establish the veracity of that which is already known, as is the case with aprotinin to reduce blood loss and transfusion. Finally, there are those, such as the use of epidural analgesia, where meta-analysis has informed us of its efficacy in reducing complications but do not and can never answer the key question “What is the incidence of epidural haematoma”? However, whilst the literature on evidence practice is steadily increasing, the great majority of cardiothoracic anaesthesia and critical care remains without any.