We studied to screen medicinal plants having hepatoprotective activity with the primary cultured rat hepatocytes intoxicated with carbon tetrachloride cytotoxicity. The lowest concentration and treatment time of carbon tetrachloride giving the greatest intoxication to the primary cultured hepatocytes were observed in 10mM and 60 minutes, respectively. GTP and GOT activity of culture broth of the primary cultured rat hepatocytes intoxicated by $CCl_4$ cytotoxicity at this condition were increased 135.9% and 178.3% compared with that of the primaries cultured hepatocytes not treated with $CCl_4$, respectively. This increased GPT activity was inhibited by glycyrrizin, which was known to have hepatoprotective activity, and the inhibition activity was dependent on the concentration of glycyrrhizin. Forty species among the extracts obtained from 117 species of medicinal plants were shown to have the hepatoprotective activity. Among these 40 species, Prunus persica, Scutellaria baicalensis, Astragalus membranaceus, Tribulus terrestris, Caragana chamlagu, Acanthopanax sessiliflorum and Achyranthes japonica were indicated a lower GPT activity than that of Glycyrrhiza uralensis containing glycyrrhizin and GPT activity of these were indicated 75.5%, 70.0%, 59.0%, 77.5%, 60.0%, 75.0% and 79.0%, respectively.