Atherosclerosis has been considered an inflammatory disease based on the finding that atherosclerotic lesion contains activated T lymphocytes reacting with oxidized low-density lipoproteins (oxLDL) and heat shock proteins (HSP); it also contains autoantigens like beta2GPI, a target of antibodies occurring in an immune-mediated thrombophilia called antiphospholipid syndrome (APS). Further support to this hypothesis comes from the cross-reactivity, which occurs between antiphospholipid antibodies (aPL) and antibodies to oxLDL. Animal experiments have shown that aPL are associated with atheroma. In addition, accelerated atherosclerosis has been detected in patients with a prototype systemic autoimmune disease, such as systemic lupus erythematosus (SLE). However, the association of APS or aPL with atherosclerosis is a matter of debate due to the small numbers of patients studied, and the fact that traditional risk factors for atherosclerosis coexist. The prevalence of APS ranges from 1.7% to 6%, and that of aPL reaches to 14% among patients with peripheral vascular disease defined on the basis of clinical outcomes. On the other hand, the prevalence of asymptomatic atherosclerosis, defined in terms of plaques in ultrasonography, reaches to 15% of patients with APS compared to 9% of SLE patients and 3% of normal controls. Among SLE patients with aPL, the prevalence of plaques ranges from 6% in premenopausal women to 31% in unselected patients. Less than 10% of APS patients express premature atherosclerosis in the absence of other risk factors. Which APS patient will develop atherosclerosis is unpredictable.