Several demographic and psychosocial variables affect assessment and treatment of chronic pain patients. The variables include demographic characteristics, life styles, family constellations, job conditions, financial status, support networks, and leisure activities. In recent years clinics and programs have emerged in a variety of configurations. Programs vary according to geography, agency, size, and training emphasis. Patients vary systematically according to program type on demographics, characteristics of pain problems, treatment history, and employment and compensation status. Findings regarding ethnic differences in responding to pain were reported among Black, Italian, Jewish, Irish, and Puerto Rican patients. While intellectual and personality variables bear some relationship to reported pain, the relationships are complex and equivocal. Several studies report Minnesota Multiphasic Personality Inventory (MMPI) results. Although the MMPI does not reliably differentiate "functional" from "organic" or predict success versus failure among pain patients, it does reflect distress level, chronicity, and adaptation to the condition. Chronic pain is an extremely complex phenomenon. Pain experience and pain behaviors are affected by interacting physical, medical, psychological, vocational, and social conditions. All these factors and their cumulative effects should be considered in order to treat chronic pain patients effectively. (Author/ABL)