Annexin II is a receptor for tissue-type plasminogen activator (t-PA) that converts plasminogen to plasmin. Although the fibrinolytic system is known to play an important role in the pathogenesis of abdominal aortic aneurysms (AAAs), the relationship between annexin II and AAA development is unknown. Therefore, we examined annexin II localization in the wall of human atherosclerotic AAAs. Specimens from 13 patients undergoing elective repair of an AAA were taken. Annexin II expression was evaluated by immunohistochemical analysis. Immunostaining results were semiquantitatively analyzed using histology scores and WinROOF software based on staining intensity. The expression of annexin II was increased and the histology score was higher in the shoulder region of the atheromatous plaque than in the atheroma and fibrous plaque regions. Annexin II appeared to have greater expression and the histology score was higher in regions where the media was preserved. Furthermore, there was a significant inverse correlation between AAA size and histology score in the fibrous plaque region. The present work demonstrates various levels of annexin II expression within the aneurysm wall. Therefore, we suggest that alteration of annexin II expression within the aortic wall may be associated with the development of an aneurysm.