Healing or successful intervention usually leads to the resolution of pain. However, in some patients biologic or psychologic symptoms associated with pain persist despite treatment or apparent healing. In cases in which the etiology is not known, persistent pain is categorized as a clinical syndrome known as "chronic pain." Organic, psychologic, and socioenvironmental factors contribute to the development of chronic pain. Major organic illnesses leading to chronic pain include headaches, back problems, arthritis, and cancer. Significant psychological reactions occur in many pain patients, with depression being the most common. Pain is often seen in patients with psychiatric disorders such as depression, anxiety, and somatization, as well as in substance abusers. Before successful management can begin, the major etiologic factors and sequelae of the chronic pain syndrome must be understood. Antidepressants, neuroleptics, anticonvulsants, nonsteroidal anti-inflammatory drugs, and hydroxyzine have been proven effective in the treatment of pain syndromes. The treatment of patients who present with chronic pain must be individualized based on a comprehensive understanding of the factors underlying the chronic pain syndrome of each patient.