This study was conducted to obtain acute information of the oral dose toxicity of lyophilized water extract of Pinelliae Rhizoma, a dried tuber of Pinellia ternata (PR) in male and female mice. In order to calculated 50% lethal dose (LD50) and approximate lethal dose (ALD), test material was once orally administered to male and female ICR mice at dose levels of 2000, 1000, 500, 250, 125 and 0 (vehicle control) ml/kg (body weight). The mortality and changes in body weight, clinical signs, gross observation, organ weight and histopathology of principle organs were monitored 14 days after treatment with PR extract. We could not find any mortalities, clinical signs, changes in the body and organ weights, gross and histopathological findings except for dose-dependent increases in the hepatic fatty change frequencies detected in PR extract 2000 and 1000mg/kg treated in both male and female mice. The results obtained in this study suggest that LD50 and approximate LD in mice after single oral dose of PR extracts were considered over 2000 mg/kg in both and female male mice, but more than 1000mg/kg of PR extracts treatment could induce slight hepatotoxicity the fatty changes in mice.