For many years clinicians have had to cope with the accusation that only 10-20% of the treatments they provide have any scientific foundation. Their interventions, in other words, are seldom "evidence based". Is the profession guilty as charged? In April, 1995, a general medical team at a university-affiliated district hospital in Oxford, UK, studied the treatments given to all 109 patients managed during that month on whom a diagnosis had been reached. Medical sources (including databases) were then searched for randomised controlled trial (RCT) evidence that the treatments were effective. The 109 primary treatments were then classified: 82% were evidence based (ie, there was RCT support [53%] or unanimity on the team about the existence of convincing non-experimental evidence [29%]). This study, which needs to be repeated in other clinical settings and for other disciplines, suggests that earlier pessimism over the extent to which evidence-based medicine is already practised is misplaced.