Endothelial dysfunction is considered an important marker in atherosclerosis, having a prognostic value. Antiphospholipid antibodies are considered prothrombotic and have recently been reported to be associated also with atherosclerosis. This study was conducted to investigate a possible association of endothelial dysfunction with various antiphospholipid autoantibodies in healthy subjects and patients with cardiovascular disease. In a single-center, prospective study, 2 groups were included. The study group included patients with cardiovascular diseases (coronary disease and/or cerebrovascular disease) and healthy subjects without apparent heart disease who were referred to the endothelial function laboratory for the assessment of endothelial function. Flow-mediated dilatation, which indicates endothelial function, and nitroglycerin-mediated vasodilatation, which indicates smooth-muscle function, were measured. The 2 groups were evaluated for autoantibodies, including anticardiolipin (aCL; immunoglobulin G [IgG], immunoglobulin M [IgM], and immunoglobulin A [IgA]), antinuclear antibody, anti–β2-glycoprotein I (IgG, IgM, and IgA), and oxidized low-density lipoprotein. One hundred seven subjects were included in the study: 45 patients (42%) and 62 healthy controls (58%). Flow-mediated dilatation was significantly lower in patients compared with healthy controls (8.0 ± 9.5% vs 8.0 ± 13.5%, p = 0.012). In addition, nitroglycerin-mediated vasodilatation was nonsignificantly lower in patients than in healthy controls (8.0 ± 13.4% vs 11.0 ± 16.7%, p = 0.084). The mean levels of anti–β2-glycoprotein I (IgG, IgM, and IgA), aCL (IgM and IgA), antinuclear antibody, and oxidized low-density lipoprotein were not different between groups. However, the mean level of IgG aCL was significantly higher in patients than in healthy controls. In conclusion, in accordance with previous reports of an association between aCL and atherosclerosis, patients with cardiovascular disease had endothelial dysfunction and elevated levels of aCL.