The etiology of fibromyalgia is not clearly understood. In recent years. a few Studies have investigated the possible role of reactive oxygen species (ROS) in the etiology and pathogenesis of fibromyalgia. The aim Of this study was to investigate plasma antioxidant vitamins, lipid peroxidation (LP). and nitric oxide (NO) levels in patients with fibromyalgia and controls. The Study was performed on the blood plasma of 30 female patients and 30 age-matched controls. After a fast of 12 h, blood samples were taken, and plasma samples were obtained for measurement of vitamins A, C, E, and P-carotene concentrations and levels of LP and NO. Concentrations of vitamins A (p < 0.01) and E (p < 0.001) were significantly lower in patients with fibromyalgia than in controls, and LP levels were significantly (p < 0.05) higher in the plasma of the Patients than in controls. Concentrations of, Vitamin C and beta-carotene and levels of NO did not change significantly. These results provide some evidence for a potential role of LP and fat-soluble antioxidants in the patients with fibromyalgia. Copyright (C) 2009 John Wiley & Sons, Ltd.