Oxidative stress and LDL modification (oxLDL) are early pro-atherogenic events. OxLDL binds beta2GPI producing immunogenic oxLDL/beta2GPI complexes. Antibodies to these complexes have been associated with arterial thrombosis in patients with systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS). Circulating oxLDL/beta2GPI complexes, IgG and IgM antibodies to these complexes were measured by ELISA in 30 SLE patients asymptomatic for cardiovascular disease (mean age 31 years) and 27 age/sex matched healthy controls. Carotid intima-media thickness (IMT) was measured by ultrasound in all patients and controls. Forty-seven percent of SLE presented plaques (median IMT of 0.65 +/- 0.12 mm) while only 7% of the controls had plaques (median IMT of 0.50 +/- 0.04 mm, P < 0.001). Median optical density (OD450nm) for oxLDL/beta2GPI complexes in SLE was 0.244 +/- 0.07, higher than controls (0.174 +/- 0.09, P < 0.001). Median OD for IgG anti-oxLDL/beta2GPI antibodies was also higher in SLE (0.297 +/- 0.26) compared to controls (0.194 +/- 0.07, P < 0.001) while the median OD for IgM antibodies in SLE (0.444 +/- 0.46) was not different than controls (0.326 +/- 0.22, P = 0.267). There was no correlation between IMT and oxLDL/beta2GPI complexes, IgG or IgM antibodies, possibly reflecting the complex interrelationship between these serologic elements and tissue factors in the arterial wall. These results support the hypothesis that oxLDL/beta2GPI complexes and IgG (not IgM) anti-oxLDL/beta2GPI antibodies contribute to the development of autoimmune-mediated atherosclerosis.