Pain–it is the most common complaint presented to physicians. Yet pain is subjective–it cannot be measured directly and is difficult to validate. Evaluating claims based on pain poses major problems for the Social Security Administration (SSA) and other disability insurers. This volume covers the epidemiology and physiology of pain; psychosocial contributions to pain and illness behavior; promising ways of assessing and measuring chronic pain and dysfunction; clinical aspects of prevention, diagnosis, treatment, and rehabilitation; and how the SSA’s benefit structure and administrative procedures may affect pain complaints.