Mouth-to-cecum transit and serum bile acid profile after ingestion of a lactulose-labeled liquid meal (440 kcal) were measured in eight patients with gallstones and a radiologically functioning gallbladder before and three to five months after cholecystectomy and in 15 controls. In the patients mouth-to-cecum transit was longer after the operation, 87.5 +/- 18.5 (mean +/- SEM) min vs 57.5 +/- 9.7 min (P less than 0.05). Mouth-to-cecum transit times before and after the operation were not different from controls (58.0 +/- 6.7 min). Serum bile acid AUCs were similar (P = NS) in patients and controls, while total bile acid and cholylglycine fasting concentrations were higher after cholecystectomy (P less than 0.05 and P less than 0.01 respectively). Cholecystectomy prolongs mouth-to-cecum transit of a liquid meal.