Aim To investigate the effects of pituitary adenylate cyclase activating polypeptide (PACAP) on vascular remodeling in atherosclerotic rabbits. Methods 60 male New Zealand rabbits were divided randomly and equally into three groups: control group,atherosclerosis (As) group and PACAP group. 5～8 rabbits of each group were sacrificed at the end of the fourth,eighth and twelfth week and the thoracaortae were collected. The segments about 0.5 cm long from the beginning, middle and end part of the above aortae were obtained to be made into paraffin sections and stained with hematoxylin eosin(HE), then the sections were observed by light microscope and the related parameters were measured by image analysis system. The rest part of the aortae were stained with Sudan Ⅳ and surveyed by naked eyes. Results Plaque area and percentage of plaque formation increased gradually with the proceeding of experiment in As group (p<0.05), and plaque mostly located in the beginning segment, decreased in the middle and end segments in turn. Lumen area varied rarely in early plaque formation, while decreased significantly at the advanced stages (p<0.05). Plaque area and maximal plaque thickness in PACAP group were smaller than those in As group, but lumen area was larger than that in As group(p<0.05). Conclusion PACAP can retard the progression of As by inhibiting negative remodeling and promoting positive remodeling.