Severe oxidative stress has been reported in leprosy patients because of malnutrition and poor immunity. The purpose of this study was to investigate the serum lipid peroxidation products, serum LDH and important free radical scavenging enzymes, i.e. superoxide dismutase (SOD), and catalase and anti-oxidant glutathione levels and total anti-oxidant status, in different types of leprosy patients. The subjects for this study were normal human volunteers (NHVs, n=14), paucibacillary leprosy patients (PB, n=18), untreated MB patients (MB1, n=18), MB patients under treatment (MB2, n=19), and MB patients released from treatment (RFT) (MB3, n=28). The levels of lipid peroxidation product, malondialdehyde (MDA), and LDH increased significantly (p<0.001) in MB (MB1, MB2, MB3) patients, and both gradually decreased with clinical improvement following MDT. The levels of SOD, catalase and glutathione, and the total anti-oxidant status decreased significantly in MB (MB1, MB2, MB3) patients (p<0.001), in comparison with NHVs. They gradually increased with clinical improvement with MDT. There was no significant variation of these parameters in PB leprosy patients in comparison with healthy volunteers. High free radical activity and low anti-oxidant levels observed in MB (MB1, MB2, MB3) leprosy patients indicate that there is an oxidative stress in MB cases, irrespective of the treatment status and suggest a suitable anti-oxidant therapy to prevent possible tissue injury.