A limited number of studies have been conducted on the bioactivity of Callophyllis japonica (C.japonica), which is a red seaweed that is traditional in the oriental diet. In this report, thehepatoprotective effect of C. japonica was studied in a carbon tetrachloride (CCl4)-inducedhepatotoxicity model in rats. A single intraperitoneal injection of 1.25 ml/kg of 20% CCl4 in oliveoil produced an elevated level of serum glutamic pyruvic transaminase (SGPT) and increasedenzyme activity of serum glutamic oxaloacetic transaminase (SGOT). Pre-treatment with C.japonica (150mg/kg/d) for 3 days in CCl4-injected rats reduced the levels of SGPT and SGOTcompared with control levels (P < 0.05), while higher doses (300 and 600 mg/kg) were ineffective.The administration of C. japonica (150 mg/kg/d) for 3 days after the CCl4 injection in rats wasineffective at reducing SGPT and SGOT. The histopathological findings in each group largelyagreed with the biochemical data. The results of this study support the suggestion that C. japonicahas a hepatoprotective effect on chemical-induced liver injury.