Interindividual differences in endorphin levels may relate to widespread changes in adaptive processes, and endorphin levels may thus be related to personality traits. In 40 patients with chronic pain syndromes of both psychogenic and organic origin, endorphin levels in cerebrospinal fluid (CSF) were determined, and the patients completed Eysenck's Personality Inventory (EPI) and the Cesarek Marke Personality Scheme. Twenty-seven of the patients also completed the Zuckerman Sensation Seeking Scale (SSS). As a comparison group 30 healthy volunteers completed the personality inventories. The chronic pain patients were characterized by guilt feelings, need for order, low need for autonomy, and low tendency toward sensation seeking. Low levels of endorphins in CSF were found in patients with high scores on all the subscales in the SSS and low scores on the neuroticism subscale in the EPI.