Duodenogastric reflux (DGR) has been suggested as an etiopathogenic factor in gastric disease in patients with gallstones. We evaluated the DGR levels in 15 patients before and after simple cholecystectomy for gallstones and compared the results with those of 15 healthy subjects. Gastric juice was obtained by continuous nasogastric suction for 24 hours. The bile acids (BA) present in the samples were quantified by thin-layer chromatography and in situ spectrofluorometry. The mean BA concentration for the control subjects was 2.25 mumol reflux/hour, whereas the mean value for the 15 patients with cholelithiasis was 8.86 mumol reflux/hour before cholecystectomy and 24.55 mumol reflux/hour after cholecystectomy. Five patients did not have detectable BA in the gastric juice in both analyses; the remaining 10 patients showed a significant increase in the BA after surgery. From these data, we conclude that gallstone disease is not always accompanied by an increased DGR. However, in patients in whom DGR is present, its level is higher than in control subjects and increases significantly after cholecystectomy. This is probably due to the greater amount of bile in the duodenum that may reflux through an incompetent pyloric channel.