Sphincter of Oddi dysfunction has been reported as a cause of acute idiopathic recurrent pancreatitis (IRP). Octreotide, a long-acting somatostatin analogue, is an antisecretory drug used in the treatment and prevention of acute pancreatitis. Its action on sphincter of Oddi motility is controversial and no data are available for IRP patients. The aim of this study was to assess sphincter of Oddi motor response to acute administration of octreotide in patients with past attacks of acute pancreatitis without identification of any evident aetiological factor. Six patients (four male, two female; mean age +/-SD, 38.8+/-9 years) suffering from acute pancreatitis for at least 3 months before the examination were submitted to sphincter of Oddi manometry. After a basal recording lasting at least 2 min, octreotide, 0.05 mg i.v., was administered and the recording repeated. Intraduodenal pressure was taken as the zero reference and the basal sphincter of Oddi pressure and amplitude and frequency of phasic contractions were calculated before and after octreotide administration. No significant pre- vs post-octreotide differences were observed in basal pressure (41.9+/-24 vs 47.5+/-33 mm Hg, respectively) or in amplitude of phasic contractions (164.6+/-33 vs 170.8+/-18 mm Hg). With a latency of about 1 min, octreotide administration caused a high-frequency phasic activity in all cases (mean frequency, 5.5+/-2.2 contractions/min before and 9.8+/-2 after octreotide; P < 0.04). After the procedure acute pancreatitis (prolonged abdominal pain and serum amylase levels more than three-fold the normal values) developed in five patients. In conclusion, our data suggest that acute administration of octreotide may induce tachyoddia and thus a rise in sphincter of Oddi pressure, with possible impairment of biliary-pancreatic outflow.