Technetium 99m diethylenetriaminepentaacetic acid-galactosyl human serum albumin is a newly developed analog ligand to asialoglycoprotein receptor, which is a hepatic cell surface receptor specific for galactose-terminated glycoproteins. Hepatic functional imaging, which yields estimates of asialoglycoprotein receptor concentration, was performed after intravenous injection of 3 mg technetium 99m diethylenetriaminepentaacetic acid-galactosyl human serum albumin. A total of 75 human subjects were studied: 6 controls without liver diseases, 51 patients with chronic liver diseases and 18 patients with acute liver diseases. In chronic liver disease the asialoglycoprotein receptor concentration significantly correlated with the clinical severity based on the criteria of the Liver Cancer Study Group of Japan (rs = -0.890, p = 0.0001). Good correlations between the asialoglycoprotein receptor concentration and conventional liver function tests were also observed. In acute liver disease the asialoglycoprotein receptor concentration correlated well with the normotest (r = 0.796, p = 0.0001), prothrombin time (r = 0.701, p = 0.0002) and total serum bilirubin (r = -0.642, p = 0.0007). We conclude that the parameter, asialoglycoprotein receptor concentration, obtained from the kinetic analysis of technetium 99m diethylenetriaminepentaacetic acid-galactosyl human serum albumin time-activity data, is a sensitive measure of functioning hepatocyte mass in acute and chronic liver disease.