The aim of the present study was to compare gallbladder emptying, gastric emptying and release of cholecystokinin (CCK), gastrin and secretin after intragastric administration of fish oil and trioleate. After intravenous injection of 99mTc-HIDA, 30 ml of a lipid labelled with 111In was administered through a gastric tube. Using dual scintigraphy with two markers, gallbladder and gastric emptying were measured simultaneously for 120 min. Plasma concentrations of gastrin, secretin and CCK, were determined throughout the period. The emptying of the gallbladder was reduced by 27% and the release of CCK by 85% after fish oil as compared with trioleate. Gastric emptying as well as the release of gastrin and secretin were similar after the two types of fat. The results suggest that the reduced gallbladder emptying after fish oil may be due to a smaller release of CCK.