AIM: Weill-Marchesani syndrome (WMS) is a rare systemic disorder with both autosomal recessive and dominant inheritances. Accumulation of reactive oxygen species such as O-2(.-), H2O2 and OH. causes lipid peroxidation (LPO), whereas antioxidant enzymes (superoxide dismutase (SOD), glutathione peroxidase (GSHPx)) mediate defence against oxidative stress. Excess tumour necrosis factor (TNF)-alpha and NO. react with O-2(.-) and cause further antioxidant depletion with an increase in mutation frequency by H2O2. This study investigated the levels of SOD, GSHPx, catalase (CAT), TNF-alpha, NO. and LPO in patients with WMS.