The purpose of this study was to investigate the acute toxicity with oral administration in ICR mice of Ohyaksungi-san fermented with Lactobacillus sp. Methods In single oral administered toxic test, four groups were administrated different dosages(0, 1250, 2500, 5000 ㎎/㎏) of fermented Ohyaksungi-san. After single oral administration, we observed number of death, clinical signs, body weight changes, hematological values and autopsy. Results Compared with the control group, we could not find any toxic signs in the mortalities, clinical signs, body weight changes, necropsy findings and hematological values in all treated groups (1250, 2500 and 5000 ㎎/㎏). Conclusions These results indicate that the LD50 value of fermented Ohyaksungi-san extract might be over 5000 ㎎/㎏ and it have no side toxic effect to ICR mice