Aim To assess the response of adventitia and adventitial cells after arterial injury. Methods Newzealand rabbits underwent balloon injury to the abdominal artery by over-sized angioplasty balloon. Adventitial changes were characterized by histochemistry, morphometry, immunohistochemistry and transmission electron microscope. Results Adventitial thickness significantly increased at all time points comparing with normal vessels. Cell density reached the maximum level at 7 d, whereas at l4 d, the cell density reverted toward the baseline. Meanwhile, the cell proliferation index rapidly increased at 3 d and 7 d respectively, and it reduced to normal level at 14 d. At 7 and 14 days after injury, The adventitia exhibited weakly positive staining for actin at 3 days, and strongly positive at 7 and 14 days. Adventitial cells displayed numerous actin microfilaments and marked dilated rough endoplasmic reticulum at 7 and 14 days after injury. Conclusions This study demonstrated the involvement of the adventitia in vascular repair process. The hypercellularity of the adventitial layer, proliferation fibroblast, and modulation of their phenotype to myofibroblast are associated with the thickness of adventitia.