Objectives : This study aimed to evaluate the single oral dose toxicity and four weeks repeated dose determination of Gamisasangja-tang (GST) in male and female Sprague-Dawley rats. Methods : In the single oral toxicity study, rats were orally administered a single dose of 0 and 5,000 mg/kg GST. There were 5 rats in each group. After single administration, mortality, clinical signs, body weight changes and gross pathological finding were observed for 14 days. In the 4-weeks repeated oral dose determination study, rats were orally administered a single dose of 0, 1,250, 2,500 or 5,000 mg/kg GST. There were 5 rats in each group. Mortality, clinical signs, body weight changes, food consumption and gross pathological finding were observed for 28 days. Organ weight, clinical chemistry and hematology were tested after 28 days. Results : There was no mortality in either of the two studies. There were also no significant differences in clinical sign, body weight, organ weights, hematological or serum chemical parameters between the GST and control groups. Conclusions : The results obtained in this study suggest that the 50% lethal dose of GST is over 5,000 mg/kg, so this finding would be expected to provide scientific evidence for the safety of GST.