Compartmentalization of Ca2+ was studied in homogenates and subcellular fractions (nuclei, mitochondria, microsomes and cytosol fraction) of rat liver tissue under conditions of chemical lesion of hepatocyte membranes caused by CCl4. The studies were carried out within 2, 24, 48, 96 and 168 hrs after the CCl4 administration. The chemical lesion of hepatocyte membranes led to considerable increase in Ca2+ concentration in the subcellular fractions studied, especially in cytosol fraction, where it reached about 424% as compared with the control level. The drastic increase of calcium concentration in cytosol appears to be due to disturbance of both Ca2+ elimination through plasmatic membrane and its mitochondrial sequestration.