Using the electron spin resonance (ESR) and probe technique, the species of reactive oxygen free radicals and the oxygen consumption were observed in the metabolic process of oxygen of leukocytes from leukemia patients and healthy persons. Results showed that weak ESR spectrum of hydroxyl radical ((*)OH) signal was detected in the leukemia patient's leukocytes, there was no significant difference in oxygen consumption with or without PMA stimulation; superoxide anion (O(2)) in normal leukocytes was detected, and oxygen consumption increased markedly compared to the normal respiration without PMA stimulation (P < 0.001). There was no significant difference in oxygen consumption between leukemic and normal leukocytes without PMA stimulation; however, it was higher in normal leukocyte than in leukemic leukoeytes after PMA stimulation (P < 0.001). These observations suggest that dysfunction of respiratory burst is existed in leukemic leukocytes, and their oxygen consumption is markedly lower than that of normal leukocytes.