The authors present the results of determinations of beta-endorphin-like immunoreactivity in the plasma carried out before and after pinpoint receptor stimulation (prs) that is acupuncture in patients with long-standing pain. No significant differences were observed in this immunoreactivity after prs, and the clinical analgesic effect was independent of the level of this immunoreactivity and its changes during these procedures. On the other hand, a positive correlation was demonstrated between plasma beta-endorphin concentration and the neuroticism index as evaluated by Eysenck's personality inventory. The reliability of this observation requires, however, confirmation in a greater material.