It has earlier been suggested that cholecystectomy, by eliminating the reservoir function of the gallbladder, will induce reflux of bile to the stomach. In the present study 23 patients were studied for duodenogastric reflux of bile acid before and 3 months after cholecystectomy. At the test the gastric contents were continuously aspirated via a nasogastric tube, collected at 15-min intervals for 2 h in the fasting patient, and analyzed for volume and bile acid concentration. The results were compared with those in 14 control subjects. Significant duodenogastric reflux of bile acid (greater than 100 mumol/h) was seen more frequently in gallstone patients than in controls. This is explained by a high prevalence of bile acid reflux in patients with a reduced or absent opacification of the gallbladder at cholecystography. Cholecystectomy increased the prevalence of bile acid reflux in the patients with well-opacified gallbladders at cholecystography. The duodenogastric reflux of bile acid in patients with a poor filling of the gallbladder at cholecystography was not further enhanced by cholecystectomy. It is concluded that gallstone patients have an increased tendency to duodenogastric reflux of bile acid. This tendency is further enhanced by removal of a functioning gallbladder. The findings may explain some of the symptoms in patients with gallstones. The reflux may also be responsible for symptoms in the so-called postcholecystectomy syndrome.