The acute toxicity of a recombinant granulocyte-macrophage colony stimulating factor (code name: LBD-005) was evaluated in both sexes of ICR mice, 5~6 weeks old, by the oral, subcutaneous and intravenous routes of administration. Based on the results of the acute toxicity study, LBD-005 was not considered to induce any toxic effect on the mice in mortalities, clinical findings, body weights and gross findings. It is suggested that $LD_50$ values in mice would be >48 mg/kg in the oral route and >24 mg/kg in the subcutaneous or intravenous route.