Brain death results in a profound physiological derangement associated with deterioration of the function of other organs. Therefore understanding of the physiologic change of brain-dead patients is important to manage organ donors. 9 brain-dead patients were studied. The mean time from donor detection to the final (second) certification of brain death was calculated. Blood pressure, heart rate, body temperature, central venous pressure, hourly urine output and PaO2/FiO2 were measured at ICU admission, first and second certification of brain death, and before starting to opera- ting room. Laboratory data were recorded at the same time, The mean time to the final certification of brain death was 27.1±11.9 hours. Hypotension, tachycardia, hypothermia, polyuria, mild hypoxemia. hypernatremia, hypokalemia, metabolic acidosis and hyperglycemia were the major complications in the period of ICU admission. We concluded that the physiologic derangements of brain-dead patients were rapidly progressed. Therefore the time to brain death certification must be reduced and intensive care of physiologic abnormality is needed during ICU stay.