Aim To assess the corelation between vascular smooth muscle cell proliferation and apoptosis, under the regulation of cell cycle, during abdominal aortic aneurysm formation and development. Methods Guinea pig-SD rat abdominal aorta xenografts were used as experimental model. Immunohistochemistry and in situ end-labeling of DNA fragments determined vascular smooth muscle cell and their proliferation and apoptosis. Cell proliferation and apoptosis index were counted with the use of computer-generated image analysis at 1,2,3,4 week after transplantation. Results Graft dilation, during 1-2 weeks, were moderate, but marked in the later 2 weeks in comparison to the controls. Vascular smooth muscle cell proliferation proceeds apoptosis by 2 weeks, and shifts to the contrary in another 2 weeks. The abdominal aortic diameter had a significant correlation with increasing vascular smooth muscle cell apoptosis in xenograft. Conclusion vascular smooth muscle cell proliferation and apoptosis is connected with abdominal aortic structure damage and remodeling, whose imbalance contributes to abdominal aortic aneurysm formation and development.