Transcutaneous electric nerve stimulation(TENS) of different frequencies were delivered through skin electrodes placed on certain acupoints of the patients. Changes of the contents of opioid peptide dynorphin A(Dyn-A) and two metabolic products of another opioid peptide methionine enkephalin(MEK), MEK1-4 and MEK2-4 were observed in human cerebral-spinal fluid(CSF). The result showed that (1) the contents of MEK2-4 and Dyn-A in the CSF of patients with acute pain were decreased significantly compared with normal control level while the content of MEK1-4 remained unchanged in patients with acute or chronic pain; (2)TENS of 2/100Hz but not 2/15Hz elevated the CSF level of Dyn-A significantly in chronic pain patients. Our previous studies performed in rats in Han's Laboratory showed that electroacupuncteure stimulation of 100-and 2-Hz increased the release of spinal Dyn-A and MEK respectively, which plays an important role in the mechanism of electroacupuncture-induced analgesia. Results obtained in the present study suggest that in patients with acute and chronic pain spinal opioid peptides can also be mobilized by peripheral electrical stimulation of specific frequencies.