This study was undertaken to clarify the intrahepatic bile flow mechanism in man. The fasting cholescintigraphy was obtained from 40 healthy controls and 5 patients with hepatolithiasis by injection of 2 m Ci of 99mTc-EHIDA. The serial analog images were recorded at each 5 min for 1 hr and the radioactivity was simultaneously counted by a computer connected with a gamma camera at 1 frame per 15 sec. Results obtained are summarized as follows: The analog images and dynamic curves obtained from 32 out of 40 controls demonstrated that the bile flow of the left hepatic duct was significantly delayed than that of the right hepatic duct, and this seemed to coincide with the high incidence of left intrahepatic gallstones. The bile flow was always hampered throughout the biliary tracts in 5 cases of hepatolithiasis regardless of location of stones. Proximal drainage (hepatic portojejunostomy) and distal drainage (transduodenal sphincteroplasty) showed excellent drainage effects on the recovery of the disturbed bile flow in those patients.