Objective: To study the effects of adenovirus-mediated Mfn2 gene transfection on the apoptosis of vascular smooth muscle cells after balloon injury of rat carotid artery. Methods: Rat common carotid arter ies were subjected to balloon injury and simultaneously infected with either Adv-rMfn2-GFP or Adv-GFP from the periarterial sheathes of vessels. The expression of Mfn2 protein was detected by immunohistochemical staining with the anti-rMfn2 polyclonal antibody. TUNEL assay was used to confirm the apoptosis cells. Neointima thickening was assessed using the intima to media area ratio (I/M) measured with a computer-based Image-Pro morphometric system. Results: Five days after surgery, the rMfn2 protein level was significantly increased in arteries infected with Adv-rMfn2-GFP compared with those from other groups. The percentage of TUNEL-positive VSMCs in Adv-rMfn2-GFP group (19.8 ± 2.1) % was markedly augmented compared with those in Adv-GFP group (9.4 ± 1.7) % or uninfected group (7.8 ± 1.5) %, while there was no detectable TUNEL-positive cells in the sham group (n = 10, P <0.01). The area of intima and intima to media area ratio (I/ M) on day 21 after balloon angioplasty were markedly attenuated in Adv-rMfn2-GFP group (n = 10, P <0.01). Conclusion: Overexpression of Mf n2 gene may induce the apoptosis of vascular smooth muscle cells after balloon injury of rat carotid artery.