The presence of liver IgG Fc receptor sites was demonstrated in the liver tissue from C-57 black mice with D-Galactosamine (GalN)-induced hepatitis by the localization of soluble immune complexes of peroxidase-antiperoxidase (PAP). Cryostat sections of liver tissues were incubated with the complexes and the peroxidase activity was revealed histochemically. In the normal liver tissue, PAP were localized on the Kupffer cells, some of the sinusoidal walls, and the liver cell membrane mainly at the side of the sinusoid. Twenty-four hours after single administration of GalN (1,500 mg/kg body weight), positive PAP reaction was mainly observed on the membrane surface of infiltrating cells in the area of hepatocellular focal necrosis, and faintly observed on the degenerative hepatic cell membrane and the sinusoidal walls. After 48 hours, these features became more remarkable, especially at the sites with severe necrotic lesions. After 72 hours, the positive reaction on the regenerative hepatic cell membranes again became distinct. At the chronic stage 13 weeks after repeated administrations of GalN and Freund's complete adjuvant, a strong positive reaction was found on swollen and multiplied Kupffer cells, and a faint one found on the liver cell membrane, especially at the periphery of the lobules; moreover, many PAP-positive infiltrated cells were found in the area of piecemeal necrosis. The relationship between liver IgG Fc receptors and the severity of liver cell necrosis is discussed.