Obstructive sleep apnea (OSA) is associated with cardiovascular morbidity and mortality and many other physiological and immunological disorders. An increase in hypoxia due to OSA may cause generation of reactive oxygen species (ROS). ROS are toxic to biomembranes and may lead to peroxidation of lipids. An increase in systemic biomarkers of inflammation and oxidative stress has been found in patients with OSA. The first aim of this study was to test the hypothesis that OSA is linked to increased oxidative stress (lipid peroxidation) and decreased antioxidant defense [superoxide dismutase (SOD)]. The second aim was to measure the serum levels of neutrophil chemokines [interleukin-8 (IL-8)], and granulocyte chemotactic protein-2 (GCP-2) in OSA patients. Twenty five patients with severe OSA and 17 healthy subjects were recruited. IL-8 and GCP-2 were measured in the serum by a specific enzyme immunoassay kit. Oxidative stress level was quantitated by measurement of thiobarbituric acid reactive substances. SOD enzymatic activity was measured by purely chemical system based on NAD(P)H oxidation. Mean SOD and lipid peroxidation concentrations of patients were not significantly different from those of control subjects (0.29+/-0.015 vs 0.31+/-0.01 U/ml and 4.64+/-0.57 vs 4.62+/-0.54 mmol/ml, respectively). Higher concentrations of IL-8 and GCP-2 were found in OSA patients (198.8+/-4.76 vs 180.83+/-3.38 and 383.34+/-46.19 vs 218+/-13.16 pg/ml, respectively, p<0.005). The present study does not support the hypothesis that OSA is linked to increased oxidative stress and decreased antioxidant defense. On the other hand, it suggests that systemic inflammation characterizes OSA patients.