This study was designed to explore the ideal dose of CCl4for chronic hepatotoxicity in Swiss albinomice as well as to verify the effective dose of silymarin for protection. Five groups of mice were prepared, within them, group (I) was served as control. The animals of group (II), (III) and (IV) were treated with 10mL of CCl4solution (10, 20 and 30% CCl4/olive oil, respectively)/kg b.w. for each three days, o.p. and during 6 weeks. Animals from group (V) were treated with silymarin by oral doses of 16mg/kg b.w. after one hour of every CCl4treatment as group (III). Serum alanine transaminase (ALT), total cholesterol (TC), liver weight/body weight ratio (L/B), liver tissue malondehydyde, protein carbonyls and histology properties were determined. The results showed that chronic hepatotoxicity induced by CCl4could be detected at CCl4concentration of 10mL CCl4solution (20% in olive oil)/Kg b.w. Beside, treatment with silymarin 16mg/Kg b.w. was verified as an effective dose for chronic hepatotoxicity protection.