The National Institute of Clinical Excellence (NICE) in the UK is responsible for producing evidence based guidelines for the treatment of most common illnesses, both physical and psychological. NICE uses a hierarchy of evidence, ranging from data from meta-analyses of randomised controlled trials (RCT's) at the apex, to the opinions of acknowledged experts at the bottom. The task of preparing guideline for depression involved us in performing clean meta-analyses of around 8,000 published RCTs of the treatment of this disorder. Where drug treatments were concerned we used three indicators of efficacy, as well as considering toxicity, tolerability and cost. We also distinguished between studies carried out in primary care, and studies in patients treated by the mental health services. We found it helpful to arrange our report in terms of a "stepped care" model, addressing the indications for patients being referred on for more specialised, and expensive, treatments. In the full guideline we included our doubts that depression was a homogenous clinical entity, and our awareness of the limitations of relying on randomised controlled trials (RCT's) as the only source of evidence. This Editorial summarises the content of the guideline on the treatment of depression and discusses how it was received and also what it did not say.