Background: Alteration in oxidative and nitrosative stress as well as antioxidant status is known to occur in carcinogenesis and during treatment of cancer with chemotherapeutic drugs. Objective: The objective of this study was to evaluate the serum levels of reduced glutathione (GSH) glutathione-s-transferase (GST) and nitric oxide (NO__ampersandsignbull;) in post-operative stage II breast cancer patients undergoing adjuvant chemotherapeutic treatment. Material and Methods: Clinically and histopathologically proven 30 stage II breast cancer patients were selected for the present study. Blood was collected after mastectomy before start of 1st adjuvant chemotherapy cycle and 3 weeks after receiving 1st cycle of chemotherapy. 30 healthy controls were selected for comparison. Serum GSH, GST and NO__ampersandsignbull; levels were estimated by spectrophotometric methods. Results: The serum level of reduced glutathione was significantly lower (P__ampersandsignlt;0.0004) whereas serum levels of GST and NO__ampersandsignbull; were significantly higher (P__ampersandsignlt;0.0001) in post-operative stage II breast cancer patients before chemotherapy as compared to healthy controls. After 3 weeks of receiving 1st adjuvant chemotherapy cycle, significant decrease in the serum levels of GSH, GST and NO__ampersandsignbull; was observed (P__ampersandsignlt;0.0001) as compared to levels before chemotherapy in these patients. Significant positive correlation was found between GSH and NO__ampersandsignbull; (r=+0.96) and GSH and GST (r= +0.91) after chemotherapy. Conclusion: The findings of the study suggests that administration of chemotherapeutic drugs in adjuvant setting in breast cancer patients causes increase in oxidative stress as indicated by decreased levels of antioxidant glutathione. The observed decrease in levels of GST and NO__ampersandsignbull; might be associated with decrease in levels of GSH in these patients after chemotherapy.