Habu venom (HV) incubated with dimercaptosuccinic acid (DMS) or thiosuccinic acid (TMA), was given subcutaneously to mice. The LD50 of HV was 19.7 mg/kg, and after treatment with TMA and DMS, it was 38.1 and 47.1 mg/kg, respectively. The logarithm concentration--mortality curve for the DMS-treated HV shifted to the right compared with the curve for crude HV. The curve for the TMA-treated HV was intermediate between these two. Decimal two mg of HV was then incubated with DMS, and such was given intramuscularly to mice. Hemorrhage and edema which occurred after administration of crude HV were markedly decreased with injection of DMS-treated HV, but the myonecrosis was not greatly affected. At 24 hr after the intramuscular dosing of 1 mg of HV into rats, lymphopenia, acute involution of lymphatic tissue, decrease in liver glycogen and lipid granules in zona fasiculata were apparent, indicating the mark of a stressor. When the DMS-treated venom was administered, the blood picture and histological findings did not differ greatly from the controls. As DMS has marked anti-HV activity, it may be used to investigate treatments for cases of Habu snake bite.