Recently, Ultrasonogram, C-T scan and imaging technique using gamma camera as well as conventional contrast study have developed for the detection of hepatobiliary diseases. Of the radioisotope imaging materials, I-131Rose Bengal and I-131-BSP have been used as hepatobiliary radiopharmaceuticals. But because the I-131 labelled has the limitation which is the undesirable physical characteristic of too high photon (364 Kev) for efficient gamma camera imaging with 100-200 low energy collimater, Tc-99(140 Kev) and I-123 (159 Kev) have been promising agents for their desirable properites. Harvey et al. have recently synthesized a technetium labelled N-substitute diminodiacetic acid derivative (Tc-99m-HIDA) as a hepatobiliary scintigraphic agent. The author studied the utilityof Tc-99m-HIDA imaging in 37 patients suspected of the hepatobiliary disease from May '80 to Sep. '81 at the YUMC Hospital. The results were as follows; 1. In normal subjects, the even radioactivity of the liver parenchyme appear at 5-min. image and the gallbladder, bile duct and the small bowel are clearly visualized within 30 min. after injection. The radioactivity of the liver parenchyme rapidly disappeared within 40 minutes. 2. The differential diagnosis of hepatocellular disease and complete obstruction was possible in jaundiced patients with hyperbilirubinemia up to 5.0 mg% and equivocal in patients with serum bilirubin level raging from 5.0 to 10.0mg%. Beyond that level, it was difficult to persuade. 3. In case of gallbladder carcinoma, there was nonvisualization of gallbladder and segmental dilatation and narrowing of bile duct. The transit time was delayed from bile duct to small bowel. 4. The gallbladder was not visualized in 5 cases of acute cholecystitis and faintly delayed visualized in 4 cases of chronic cholecystitis. 5. The anatomical abnormalities of the bile duct were disclosed in two cases of choledochal cyst and one case of traumatic bile leakage.