The predictive value of different preoperative provocation tests and operative biliary manometry was studied in a series of 22 patients undergoing sphincteroplasty for suspected spastic sphincter of Oddi (SPO). The result of the operation was good in 59%, 54%, and 71% of patients in groups with a positive codein test, a positive endoscopic retrograde cholangiopancreatography filling pain sign, and positive fentanyl test, respectively. Common bile duct pressure (CBDP) did not differ significantly between the SPO spasm group and control patients, but in the fentanyl test the CBDP elevation was significantly higher (p less than 0.01) than in controls (7.7 versus 3.3 mm Hg). It was concluded that the operative fentanyl test seems to be useful in predicting the response to surgery (sphincteroplasty) in patients with post-cholecystectomy biliary-type pain and suspected SPO spasm.