#### Summary points Obsessive-compulsive disorder (OCD) is characterised by the presence of obsessions or compulsions, or commonly of both. OCD is the fourth most common mental disorder after depression, alcohol/substance misuse, and social phobia, with a lifetime prevalence in community surveys of 1.6%.1 The severity of OCD differs markedly from one person to another. People are often able to hide their OCD, even from their own family, although it can cause problems in relationships and interfere with the ability to study or work. Health consequences can also occur: fear of contamination can, for example, prevent the accessing of appropriate health services or lead to dermatitis from excessive washing. When the disorder starts in childhood or adolescence, young people may avoid socialising with peers or become unable to live independently. The World Health Organization ranks OCD as one of the 10 most handicapping conditions by lost income and decreased quality of life.2 This clinical review summarises the evidence on how to recognise, assess, and manage people with OCD. #### Sources and selection criteria We referred to published systematic reviews, including the treatment guideline from the National Institute for Health and Care Excellence (2005) and the obsessive compulsive disorder evidence update (2013). We identified reviews by searches for “compulsive behavior”, “obsessive-compulsive disorder”, “obsessive behavior”, “compulsions”, “obsessions”, “obsessive compulsive …