Chemotherapeutic agents used in patients with cancer cause to generate the enormous amounts of free radicals associated with cell injury. In this study we assess the effects of chemotherapy regimen on oxidant/antioxidant status in patients with acute myeloid leukemia (AML). 38 newly diagnosed patients with acute myeloid leukemia were recruited in this study. All patients received cytarabine and daunorubicin as chemotherapy regimen. Plasma levels of malondialdehyde (MDA), total antioxidant status (TAS), and the levels of erythrocyte activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx) were determined before chemotherapy and 14 days after chemotherapy with cytarabine and daunorubicin. Plasma MDA concentrations increased significantly (from 2.68±0.89 nmol/L to 3.14±1.29 nmol/L) during the 14days post-chemotherapy period (P=0.04). Plasma TAS concentrations changed with chemotherapy from 1.09±0.15 mmol/L to 1.02±0.14 mmol/L with P=0.005. Erythrocyte SOD and GPX activity decreased overtime from 1157.24±543.61 U/g Hb to 984.01±419.09 U/g Hb (P=0.04) and 46.96±13.70 U/g Hb to 41.40±6.44 U/g Hb (P=0.02) respectively. We report here that there is an increase in malondialdehyde levels and a decrease in the levels of antioxidant enzymes and total antioxidant status. This suggests that chemotherapy causes these changes as a result of enormous production of reactive oxygen species in the patients with AML. Antioxidant supplementation must be approached with caution because of the probability of reduction the therapeutic efficacy of these cytotoxic drugs.