Psoriasis is associated with changes in plasma lipid and lipoproteins, which may play a role in the development of occlusive vascular disease. The oxidation of low-density Lipoprotein (LDL) is considered a key event in the development and progression of atherosclerosis. Autoantibodies against oxidized LDL (auAb-oxLDL) may contribute to understanding the relationship between oxidative processes and development of atherosclerosis. Thirty-three patients with psoriasis and 30 matched control subjects were investigated. LDL oxidation was evaluated as the presence of autoantibodies against LDL oxidatively modified with Cu++, by an ELISA system in the patients and control sera. AuAb-ox LDL levels of the patients were found to be significantly increased compared with a control group. 42% of the patients and 3.3% of the control subjects had higher auAb-ox LDL levels than the cut-off point (352 mU/ml). The levels of auAb-ox LDL were found to be correlated with PASI score (r = 0.67, p < 0.01). Also, The antibody level was found to be correlated with polymorphonuclear elastase and alpha-1 antitrypsin levels (r = 0.58, p < 0.05; r = 0.51, p < 0.05, respectively). It was concluded that increased levels of auAb-oxLDL in the psoriatic patients may be a consequence of the interaction between imbalance of oxidant-antioxidant system and lipoproteins, and the measurement of auAb-oxLDL in the patients may mirror in vivo occurrence of oxidative processes. (C) 1999 Elsevier Science B.V. All rights reserved.