The current discussion about the NICE head injury guidelines illustrates both the strengths and the weaknesses of the system of national guidelines for the NHS. We are still on the learning curve of how we should use this national advice in emergency medicine practice. When there is good evidence that tells that a treatment works or that a treatment does not work a guideline is easy to write. However, when there is weak evidence, as the research has not been done, writing a guideline becomes more difficult.¹ Simply leaving a gap in the guideline would not be useful, however the “best evidence available” becomes a consensus opinion among experts. Different groups of experts may come to different opinions and an individual emergency physician may, because of personal clinical experiences or particular local circumstances, disagree with the consensus. Guideline developers recognise that there is no way of telling …