BACKGROUND/AIMS: This study was designed to evaluate the effects of electroacupuncture on the sphincter of Oddi (SO) motility in humans and to correlate the manometric findings with plasma cholecystokinin (CCK) levels. METHODS: Eleven patients (M: F= 5: 6) who had various kinds of biliary disorders were enrolled. SO motility was monitored with a conventional low-compliant continously perfused technique using ERCP (n=9) or percutaneous transhepatic cholangioscope (n=2). After baseline monitoring for phasic wave contractions of SO, electroacupuncture was applied at a specific acupoint, GB 34, in these 11 patients. A nonspecific acupoint 5 cm away from GB 34 was selected as a control. Manometric parameters of SO were also checked in 6 subjects during stimulation of the control acupoint. CCK plasma levels were measured during the time course of electroacupuncture stimulation. RESULTS: All the manometric parameters including the basal pressure of SO, amplitude, frequency and duration of phasic wave contraction of SO were significantly decreased (p < 0.05) during electroacupuncture stimulation. The inhibition of SO contractility was accompanied by increased CCK plasma levels. After removal of electroacupuncture stimulation, restoration of amplitude and duration to basal condition were noted. A tendency towards the return of SO contractility was also observed in basal pressure and frequency. Stimulation of the control acupoint, however, did not affect the SO contractility and plasma CCK levels. CONCLUSIONS: Electroacupuncture stimulation of acupoint GB 34 showed reversible inhibition of SO contraction in humans. We speculate that the response of SO to electroacupuncture stimulation may be mediated by some neurohormonal mechanisms including CCK release.