(188)Re/(186)Re-N,N-bis(2-mercaptoethyl)-N',N'-diethylethylenediamine-labeled pegylated liposome ((188)Re-BMEDA-liposome) has been proven as a promising candidate for cancer therapy in tumor-rodent models. (188)Re-BMEDA complexes should be prepared for the radiolabeling of liposomes. This article describes the acute toxicity of BMEDA in Imprinting Control Region (ICR) mice. Treated mice were administered with BMEDA at dose levels of 3, 6, 9, and 12 mg/kg, with a dose volume of 10 mL/kg. The control mice were administered 10 mL/kg of vehicle control. The mice were observed for 14 days. Observations included mortality, clinical signs, total body-weight gains, food consumption, and gross necropsy findings. BMEDA exerted no adverse toxic effects in ICR mice at dose levels 3 mg/kg, which are up to 360,000 times higher than the intended human dose. The lethal-dose (LD(50)) value of BMEDA was 8.13 and 8.68 mg/kg in male and female mice, respectively.