Intraluminal pressure of sphincter of Oddi (SO) was measured in awake patients who had undergone cholecystectomy and T-tube drainage for cholecystocholedocholithiasis. Pressure measurement was carried out using microtransducer which was inserted through sinus tract under cholangioscopy after removing T-tube. Mean value of the basal pressure was 12.0 +/- 1.5 mmHg, the amplitude of the phasic contraction was 55.2 +/- 4.4 mmHg and the frequency of the phasic contraction was 4.2 +/- 0.3 cycle/min. Intravenous administration of caerulein or atropine caused marked decrease in the amplitude and the frequency of the phasic contraction of SO, whereas pentazocine caused marked increase in the basal pressure, the amplitude and the frequency of the phasic contraction of SO. Naloxone alone did not affect the phasic contraction of SO, but it reduced the increased amplitude and frequency of the phasic contraction of SO caused by pentazocine. In conclusion, cholinergic nerves, excitatory nerves mediated by opioid receptors and non-cholinergic non-adrenergic inhibitory nerves may modulate spontaneous motor activity of human sphincter of Oddi.