Until the 1960s, pain was considered an inevitable sensory response to tissue damage. There was little room for the affective dimension of this ubiquitous experience, and none whatsoever for the effects of genetic differences, past experience, anxiety, or expectation. In recent years, great advances have been made in our understanding of the mechanisms that underlie pain and in the treatment of people who complain of pain. The roles of factors outside the patient's body have also been clarified. Pain is probably the most common symptomatic reason to seek medical consultation. All of us have headaches, burns, cuts, and other pains at some time during childhood and adult life. Individuals who undergo surgery are almost certain to have postoperative pain. Ageing is also associated with an increased likelihood of chronic pain. Health-care expenditures for chronic pain are enormous, rivalled only by the costs of wage replacement and welfare programmes for those who do not work because of pain. Despite improved knowledge of underlying mechanisms and better treatments, many people who have chronic pain receive inadequate care.