Pain is one of the leading reasons why patients seek medical care. Chronic pain—pain that persists for three months—is a significant source of human suffering and disability. However, the prevalence of chronic pain as a health problem is not well reflected in standard health service data. In large part this is due to the way it has been coded. The main coding system for medical conditions used in Australia is he International Classification of Diseases (ICD) published by the World Health Organization (WHO). Unfortunately, these have failed to reflect the phenomenon of chronic pain, such that related conditions were categorised in an unsystematic and often obscure manner.