BACKGROUND: What are the successful factors of the establishment of the thread-blocking method for focal cerebral ischemia/reperfusion mouse models?OBJECTIVE: To study the effects of strain, body mass, and thread tip preparation for the establishment of focal cerebral ischemia mouse models by using middle cerebral artery occlusion (MCAO).DESIGN: Observational contrast animal study.SETTING: Gulou Hospital, Medical College of Nanjing University.MATERIALS: ①　The following experiment was performed at the Animal Experimental Center, Gulou Hospital Affiliated to Medical College of Nanjing University from December 2006 to April 2007. Sixty male white Kunming mice, whose body masses were 18–22 g (n =40), 25–29 g (n =10) and 30–33 g (n =10), as well as 10 male C57BL/6J mice, whose body mass was 18–22 g, were provided by the Animal Experimental Center, Gulou Hospital Affiliated to Medical College of Nanjing University. All mice were 10–12 weeks old. The project received confirmed consent from the local ethics committee. ②Experimental materials: tripheryltetrazolium hydrochloride (TTC) and 0.1% poly-L-lysine were provided by Sigma Company, USA; citromint was provided by Shanghai Lingfeng Chemical Company Limited. METHODS: ① Strain comparison: Ten white Kunming mice (weighing 18–22 g) and ten C57BL/6J mice (weighing 18–22 g) were selected. ② Comparison of body mass: Thirty white Kunming mice, whose body masses were 18–22 g (n =10), 25–30 g (n =10), and 30–35 g (n =10), were divided into groups. ③ Comparison of thread tip preparation: White Kunming mice weighing 18–22 g were divided into a poly-L-lysine line group and general line group, with 10 mice in each group. Mice in these two groups, which were respectively treated with poly-L-lysine or nothing, underwent MCAO. ④ All experimental mice received MCAO. Three hours after ischemia, and 24 hours after reperfusion, neurological deficit scores were measured and a success rate of model establishment was calculated. In addition, after sacrifice, sample tissues were cut into coronal sections to calculate the cerebral infarction area. MAIN OUTCOME MEASURES: ① Success rate of model establishment and cerebral infarction area.② Neurological deficit scores.RESULTS: Sixty white Kunming mice and 10 C57BL/6J mice were included in the final analysis. ① Strain comparison: The cerebral infarction area of white Kunming mice was larger than the C57BL/6J mice, and the neurological deficit scores of white Kunming mice were greater than those of the C57BL/6J mice (P < 0.05). ② Comparison of body mass: A success rate of model establishment in white Kunming mice weighing 18–22 g was higher than in white Kunming mice weighing 25–30 g or 30–35 g (P < 0.05). ③ Comparison of thread tip preparation: The cerebral infarction area of mice in the poly-L-lysine line group was larger than in mice in the general line group. The neurological deficit scores of mice in the poly-L-lysine line group were greater than in mice in the general line group (P < 0.05). CONCLUSION: Strain, body mass, and thread tip preparation can affect the establishment success rate of a focal cerebral ischemia mouse model using MCAO.