The liver protective effect of Aicaphosphate in CC1(4)-induced acute, as well as CC1(4)-and thioacetamide-induced subacute and chronic liver damages is demonstrated. The effect of the protective drugs was studied in the forms of pre-, simultaneous and delayed treatment in acute and chronic liver damages induced by various toxic agents. The degree of liver damage was determined by morphological and biochemical methods, complementary to each other. For the completion of histological studies and morphometry used for the determination of the degree of fibrosis biochemical investigations are performed. In acute liver damage the determination of DNA, protein and lipid contents of the liver tissue and the radioactive aminoacid incorporation rate should be carried out with a simultaneous analysis of the serum enzymes. In chronic liver damage, the measurement of the hydroxyproline and DNA contents of the liver give useful data for the determination of the severity of the lesion and the effect of the protective drugs, respectively.