The object of this study was to evaluate the single dose toxicity of Kong-Jin-Dan (KJD), a polyherbal formula in male and female mice. KJD was administered to female and male ICR mice as an oral dose of 2000, 1000 and 500 mg/kg (body wt.) according to the recommendation of KFDA Guidelines. Animals were monitored for the mortality and changes in body weight, clinical signs and gross observation during 14 days after dosing, upon necropsy, organ weight and histopathology of 12 principle organs were examined. As results, we could not find any mortality, clinical signs, and changes in the body and organ weight except for increases of lymphoid organ weights in KJD-dosing groups. These increases of lymphoid organ weights considered that related to the immune modulate effect of KJD not toxicological signs. In addition, no KJD-treatment related abnormal gross findings and changes in histopathology of principle organs were detected except for some sporadic accidental findings. The results obtained in this study suggest that the KJD does not cause any toxicological signs. The $LD_{50}$ and approximate LD of KJD extracts in both female and male mice were considered as over 2000 mg/kg.