This study was carried out to evaluate the three months subacute intravenous toxicity of water soluble dimethyl dimethoxy biphenylate derivative (DDB-S), a newly formulated therapeutic agent for hepatitis, in Beagle dogs. Groups of 12 male and 12 female dogs were given different dosage of DDB-S, 10 mg/kg/day (high dose group), 5 mg/kg/day (middle dose group), 2.5 mg/kg/day (low dose group) and 0 mg/kg/day (control group) for three months by intravenous route. 1n the three months intravenous toxicity study, there were neither dead animals nor significant changes of body weights during the experimental period. 1n addition to, no significant DDB-S related changes were found in clinical signs, urinalysis and other findings. Statistical changes were observed in hematological. biochemical, partial thromboplastin time (PIT) and organ weight parameters of treated groups. However, these alteration had no relationship with dosage. No histopathological lesions were observed in both control and treated animals. Above data suggest that no observed adverse effect level of test materials in Beagle dogs might be over 10 mg/kg/day in this study.