Over the last few years,there has been increasing interest in the investigation of the pathogenesis of AAA, and a role for some novel risk factors, in particular thrombophilic risk factors, has been suggested. The aim of this study was to evaluate a number of thrombophilic parameters in a large group of patients with AAA. In 438 patients with AAA, and in 438 healthy subjects, selected to be comparable for age and gender with patients and without instrumental evidence of AAA, a pattern of thrombophilic parameters [homocysteine (Hcy), lipoprotein (a) [Lp(a)], plasminogen activator inhibitor-1 (PAI-1), anticardiolipin antibodies (ACA), MTHFR C677T polymorphism, prothrombin gene G20210A variant and FactorV Leiden mutation] has been evaluated. A significant difference for Hcy, PAI-1 and Lp(a) plasma levels has been observed between patients and controls. After adjustment for the traditional cardiovascular risk factors, a significant increased risk of having AAA has been observed for high levels of Hcy (OR: 7.8; p<0.0001), Lp(a) (OR: 2.4; p<0.0001) and PAI-1 (OR: 3.2; p<0.0001). The association has been confirmed after exclusion of patients with other localization of atherosclerosis. Moreover, a significant association between larger abdominal aortic diameters and the number of thrombophilic parameters has been reported (r = 0.13; p = 0.005). In conclusion, a significant association between abnormal levels of some metabolic parameters related to thrombosis such as Hcy, Lp(a) and PAI-1 and AAA has been observed.