The aim of this study was to comparatively evaluate oxidative status of ankylosing spondylitis (AS) patients receiving anti-tumor necrosis factor (TNF) or non-steroid anti-inflammatory drugs (NSAID). Forty-seven patients with AS and 27 healthy controls were enrolled. Of these, 23 were on anti-TNF (group 1) and 24 on NSAIDs (group 2). Groups 1 and 2 were consisted of matched patients with respect to age, gender, body mass index, disease duration, C-reactive protein, erythrocyte sedimentation rate, total cholesterol, and Bath Ankylosing Spondylitis Disease Activity Index. Mean duration of treatment for patients in group 1 was 12.6 +/- 6.8 months. Serum total antioxidative status (TAS) and total oxidative status (TOS) levels were determined using new automated methods. Oxidative stress index (OSI) was calculated. The groups' carotid intima-media thicknesses (IMT-C) were also measured using ultrasonography. Group 1 had the highest TAS and lowest TOS levels. The TOS levels of group 1 was lower than the control, while group 2 being higher than controls. The difference in TOS levels between group 1 and group 2 was statistically significant (p = 0.040). OSI values were highest in group 2 and lowest in group 1. There was no significant correlation between oxidant/antioxidant parameters and IMT-C for group 1 (r = -0.30, p = 0.198 for OSI; r = 0.22, p = 0.366 for TAS; r = -0.22, p = 0.361 for TOS). This is the first study to evaluate total oxidative/antioxidative status in patients with AS on anti-TNF agent. These results clearly indicate positive effects of anti-TNF treatment on oxidative status of AS patients. The limited effects of NSAIDs compared with controls may be due to excess impaired oxidative status in the patients in this study.