Objectives : This study was conducted to investigate the safety of Bangpungtongsung-san in rats. Methods : The safety of this prescription on acute toxicity was evaluated by single dose toxicity study. Rats were orally administrated in a single dose of 0 and 2,000 mg/kg(limited dose) Bangpungtongsung-san. There were 7 rats in each groups. All animals were sacrificed after 14 days of treatment. After single administration, mortality, clinical signs, and body weight changes were observed for 14 days. Three parameters(autopsy finding, clinical chemistry, and hematology) were tested on the last day. Results : In this study with rats, Bangpungtongsung-san treatment did not show any acute toxicity. No mortality was noted for 14 days of treatment. There were no adverse effects on clinical signs, body weight changes, and autopsy finding at all treatment groups. The clinical chemistry parameters attesting to liver and kidney functions as well as the hematological parameters were within the normal ranges. Conclusions : It is considered that $LD_{50}$ of Bangpungtongsung-san is over 2,000 mg/kg in oral administration by rats. This finding of the safety of Bangpungtongsung-san is expected to strengthen the position of this prescription as nontoxic medicine.