The concept of brain death is widely accepted in most countries. However, there are differences in the criteria for the diagnosis of brain death. In Taiwan, the diagnostic criteria of brain death has just been established. These criteria require strict preconditions to be fulfilled, necessary exclusions to be made, and adequate time of observation to ensure the irremediability of the disease. Tests of brainstem reflexes and apnea are then performed and should be repeated at an interval of at least 4 hours to establish the diagnosis. This prospective study was undertaken in order to examine the reliability of the present criteria. A total of 79 comatose patients (57 males and 22 females) on the ventilator were collected. Their ages ranged from 2.3 to 89 years, with a mean of 46.3 +/- 20.3 years. The preconditions or exclusions were not fulfilled in 5 patients (3 with drug intoxication, 1 with septicemia, and 1 due to an unknown cause). Among them, 1 with alcohol intoxication recovered well. Of 16 patients with hypoxic/ischemic brain damage, brain death was diagnosed in only 2; in the remaining 14 patients, 6 became vegetative and 8 died from cardiac arrest. Fifty-eight patients sustained structural brain damage, and brain death was diagnosed in 50 of these patients. The most frequent cause of brain death was head injury (31 cases), followed by intracerebral hemorrhage (11 cases). Of the 52 patients fulfilling the criteria of brain death, all sustained cardiac asystole in a limited interval of time (96% in 7 days).(ABSTRACT TRUNCATED AT 250 WORDS)