This study was performed to investigate the acute toxicity of PEG-hemoglobin SB1, a blood substitute, in beagle dogs. The male and female dogs were administered intravenously at the doses of 0.4375, 0.875 and 1.75 g/kg body weight, respectively. After a single intravenous administration of SB1 to dogs, we observed them daily for 2 weeks. SB1 did not induce any toxic signs in the mortalities, clinical signs, body weight changes, and gross necropsy findings of dogs. Based on these results, acute toxicity, dogs SB1 may have no side effect and its $LD_{50}$ value may be over 1.75 g/kg (25 ml/kg) of body weight in dogs.