 Background and study aims In primary care between 20 and 40 of patients have medically unexplained physical symptoms. The term medically unexplained symptoms MUS is commonly used by health care professionals. However a survey of a healthy population and a separate survey of patients with chronic fatigue syndrome CFS suggested that the term persistent physical symptoms PPS was the preferred term. The term PPS may have its drawbacks, but it will used for the rest of this document to cover MUS as well as any other terms that may be used in the literature and clinical settings to refer to these symptoms. In secondary care, about 50 of patients have PPS, in many specialties. PPS are associated with profound disability and high health care costs. Around 50 of sufferers have co-morbid anxiety and depression and sleep anxiety. Left untreated, the prognosis of these patients is poor. 