Experimental research has recently shown that acupuncture induces the formation of opioid-like peptides (OLPs) in animals. In order to provide further evidence, we tested the beta-endorphin levels and other parameters (VIP, lymphocyte subsets, NK cells and monocyte phagocytosis) in a group of 90 patients suffering from various painful disorders treated with acupuncture. Zusanli (St 36) and Hegu (LI 4) acupoints were selected. A homogeneous group of 30 subjects was used as control. Evaluation of the above parameters was made with 3 series of blood tests before treatment, 30 minutes and 24 hours after acupuncture treatment. In the acupuncture group, the following results were achieved: 1) A considerable increase in beta-endorphin levels remained high even 24 hours after acupuncture treatment. In addition, we demonstrated an inverted correlation between beta-endorphins and VIP; 2) 30 minutes after acupuncture session, 80% of the treated patients showed a significant increase of CD3 and CD4 values and an increase of CD8 24 hours after stimulation; 3) Monocyte phagocytosis was increased in 45% of the treated subjects 30 minutes from starting treatment, and in 100% of them after 24 hours. The percentage of NK cells was also increased in 40% of cases after 30 minutes, and in 50% after 24 hours. However, in the control group, no such significant changes in immune parameters were found.