The present study was conducted in eighteen bitches aged between 2 and 6 years brought to Madras Veterinary College Teaching Hospital, Chennai and diagnosed with open cervix pyometra. Group I (n=6) bitches were treated with Cloprostenol @ 5 µg/kg bwt SC and cabergoline @ 5 µg/kg bwt orally once daily for 7 days. Group II (n=6) bitches were treated Dinoprost tromethamine intravaginally in to the vaginal lumen at the dose rate of 150 µg/kg bwt for 7 days. Group III (n=6) bitches were treated surgically by ovariohysterectomy. Group IV (n=6) served as healthy control group. Serum samples were collected from all bitches at weekly intervals and serum levels of oxidative stress markers (Superoxide dismutase, Glutathione peroxidase, Catalase, Thiobarbituric acid reactive substances) were analysed using ELISA method. Results showed reduced levels of antioxidant enzymes and elevated levels of lipid peroxidation metabolite (TBARS) in all the treatment groups. Oxidative stress was reduced by 3 weeks in all treatment groups. Hence, it was concluded that pyometra produces predominant oxidative stress and surgical treatment of pyometra reduced oxidative stress to much better extent when compared to medical treatment.