This study was undertaken to investigate if there is a disparity in the antioxidant status and the ability of superoxide anion (O 2 − ) generation in the patients with acute myeloid leukemia (AML).The peripheral blood samples from thirty AML patients and thirty-six healthy subjects were collected and leukocytes, erythrocytes and plasma were separated for use in various parameter measurements.The generation of O 2 − , as reflected by lucigenin-based CL (LBCL), by the leukocytes of patients with AML was found to be significantly elevated either in resting or stimuli-elicited condition as compared with that of healthy controls (p<0.05). Coincidentally, these data were matched up with the suppressed SOD activities, notably in Cu/Zn SOD isoform found in AML patients (p<0.05). Conversely, SOD and GPx activities in erythrocytes of patients with AML were shown to be significantly higher than their normal counterparts (p<0.05).These data suggest that altered expression of antioxidant enzymes and higher capability of O 2 − generation by leukocytes seem to be a distinct feature of AML.