Hepatobiliary scintigraphy with the 99mTc-labeled iminodiacetic acid derivatives has been shown to be useful in the evaluation of biliary tract diseases, especially for the diagnosis of acute cholecystitis. Little emphasis has been placed on the importance of the hepatic parenchymal image that occurs early in the imaging sequence. To determine what information can be obtained from the hepatic parenchymal image, a comparison was carried out of sulfur colloid and iminodiacetic acid images in 50 patients with focal defects. In 46 of 50 patients, the number and position of lesions on the two studies were similar, while in four patients the images were discordant. In addition to being very similar in lesion detection, the iminodiacetic acid scans also allowed more specificity in the later imaging (biliary phase) in 13 cases. The value of iminodiacetic acid derivatives in the evaluation of some biliary tract disorders has been established; considerable value can also be obtained by close inspection of the hepatic parenchymal image as well.