The aim of this study was to determine the status and the role of oxidative stress and antioxidant defenses in patients with Buerger disease and atherosclerotic peripheral arterial occlusive disease (PAOD). Seventy-three subjects resembling each other in general characteristics were involved in the study: 21 with lower extremity PAOD (mean age 53.05 +/- 10.8 years, 17 men and four women), 22 with Buerger disease (mean age 38.59 +/- 6.4 years, 19 men and three women), and 30 healthy volunteers (mean age 38.59 +/- 6.4 years, 22 men and eight women). We measured the levels of plasma malondialdehyde (MDA), paraoxonase (PON1), protein carbonyls, arylesterase, nitric oxide (NO), serum oxidized low-density lipoprotein (ox-LDL) and MDA, glutathione (GSH), glutathione reductase (GSH-red), glutathione peroxidase (GSH-px), superoxide dismutase (SOD), and catalase (CAT) in erythrocytes. Plasma protein carbonyls, serum ox-LDL, and plasma and erythrocyte MDA were significantly high in the Buerger disease group compared to the PAOD and control groups (p < 0.001). Plasma PON1 levels and GSH and GSH-px levels in erythrocytes in the Buerger disease group were significantly low compared to the PAOD and control groups (p < 0.001). GSH-red, SOD, and CAT levels in erythrocytes in the Buerger disease group were significantly lowcompared to the PAOD group (p < 0.01, p < 0.001, and p < 0.001, respectively). NO levels were significantly lower in the PAOD group compared to the control group (p < 0.05). The balance between oxidative stress and antioxidant capacity is more seriously impaired in Buerger disease than PAOD.