Hepatobiliary scintigraphy with 99Tc(m)-diethyl-iodo-HIDA (IODIDA), an iminodiacetic acid derivative, is used to assess hepatocyte function and to visualize the hepatobiliary system. The aim of this study was to evaluate whether it is possible to describe liver function by calculating the clearance rate of IODIDA from the blood. Clearance rate was evaluated in 18 liver transplant patients (28 studies) and 11 healthy volunteers (11 studies). Two different clearance rates were calculated: the clearance of IODIDA from the blood due to liver uptake and the total clearance of IODIDA from the blood due to all possible routes of elimination. Both for the healthy controls and the liver transplant patients, there was an excellent correlation between these two methods (r = 0.92 and r = 0.93, respectively), indicating that the liver is the only essential pathway for elimination of IODIDA from the blood. The difference in clearance rate between healthy controls and liver transplant patients was highly significant (P < 0.01), corresponding to the clinical condition of the two groups. We conclude that the clearance rate of IODIDA, based on a simple measurement from the time-activity curve derived from a blood pool region of interest, is a reliable test of liver function.