Cardiac syndrome X (CSX) is characterized by chest pain, typical angina pectoris, abnormal exercise test result and normal coronary arteries. Microvascular dysfunction and enhanced oxidative stress are the mechanisms suspected to play an important role in the pathogenesis of CSX. Thus we aimed to evaluate the oxidative stress status of 28 patients with CSX (14 male/14 female, mean age 49.5 ± 9.3 years) and 24 age-and gender-matched healthy controls (10 male/14 female, mean age 45.6 ± 5.7 years). Blood samples were drawn for measurement of malodialdehyde (MDA), as a marker of lipid peroxidation, glutathione (GSH) and superoxide dismutase (SOD) activity, as antioxidant markers and ferric reducing ability of plasma (FRAP), as a marker of total antioxidant capacity. There was significant increase in the levels of MDA in CSX patients comparing to controls (3.8 ± 0.12 vs 3.3 ± 0.14 mM, respectively; p = 0.006). But the levels of FRAP in CSX patients were significantly lower than those controls (504 ± 19 vs 568 ± 26 µM, respectively; p = 0.046). Also, GSH levels and SOD activity in patients were significantly lower than those of the controls (GSH: 133.6 ± 5.4 vs 152.5 ± 7.8 mmol/g Hb, p = 0.048; SOD: 386 ± 34 vs 578 ± 38 U/g Hb, p = 0.0001). It may be concluded that there is systemic oxidative stress in CSX patients. Considerable changes of antioxidant concentrations, indicating a compensatory mechanism to cope with increased oxidative stress in CSX patients and the body's antioxidant defence mechanisms try to minimize oxidative stress damage.