Psoriasis is a immune mediated disease that affects skin characterized by hyperproliferation and inflammation of the skin. It is the most common chronic inflammatory skin disease, affecting about 2% of the general population. Skin is a major target of oxidative stress due to reactive oxygen species (ROS). This study was aimed to show that ROS play a significant role in pathogenesis of psoriasis. 40 cases and 40 controls between age group of 25 – 60 were taken. The levels of serum manoldialdehyde (MDA) and nitric oxide (NO) were significantly increased and superoxide dismutase (SOD) and Total Antioxidant Capacity (TAC),estimated by Ferric Reducing Antioxidant Power (FRAP) assay were decreased as compared to normal subjects. This study provides an evidence of an increase in reactive oxygen species (ROS) production and decreased antioxidant defences in psoriasis.