The effectiveness of electroacupuncture (EA) stimulation in suppressing the morphine abstinence syndrome was studied. Male Wistar rats were made dependent on morphine either by multiple injections or pellet implantation. EA of 2 Hz or 100 Hz was administered for 30 min followed by naloxone challenge (0.5 mg/kg, i.p.) and the withdrawal syndrome was scored for a period of 45 min. In rats receiving multiple injection regime, 100-Hz EA produced a statistically significant suppression of wet shakes (-61%), teeth chattering (-59%), escape attempts (-48%), weight loss (-3.3%) and penile licking (-28%) (P < 0.05). EA of 2 Hz produced only a mild but significant suppression in escape attempts (-42%) and wet shakes (-31%). Similar results were obtained in rats receiving pellet implantation. Since 100-Hz EA has been shown to accelerate the release of dynorphins in the CNS, the results seem to be compatible with the notion that dynorphin may play an important role in suppressing the opioid withdrawal syndrome.