The organ distribution data for the two hepatobiliary agents HIDA and p-butyl- IDA in mice showed substantial differences in the extent and rate of hepatobiliary clearance of radioactivity. 99mTc-HIDA and 99mTc-p-butyl-IDA were used in computer assisted serial hepatobiliary scintigraphy. In normal subjects, the data of dynamic studies showed that the kidneys were no longer seen after 2.5 min with p-butyl-IDA. Liver radioactivity decreased significantly after 10 min with HIDA compared to 35 min with p-butyl-IDA. The gall bladder was always visualized at the 10-12th min and the 25-30th min with HIDA and p-butyl-IDA respectively. 99mTc-HIDA provided superior hepatic duct images.