Recently it was suggested that hepatic encephalopathy (HE) is mediated by an increased GABA-ergic tone. The logical consequence of such a hypothesis is the use of antagonists of the GABA -benzodiazepine receptor for treatment of HE. The experience with these drugs in human HE is limited. In order to get an estimate of the efficacy of this type of drug in humans 20 consecutive episodes of HE in 17 patients with acute or chronic liver failure were treated with flumazenil. All patients entered into the study were encephalopathic for up to 120 hours and failed to respond to conventional therapy. After an observation period of 8 hours, 15 mg of flumazenil were infused intravenously over 3 hours. Before and after treatment patients were examined neurologically and the Glasgow coma scale was calculated. In addition, somatosensory evoked potentials were recorded. In 5 out of 11 episodes in 10 patients with fulminant hepatic failure and in 7 out of 9 episodes in 7 patients with cirrhosis an unequivocal amelioration of HE was observed. The response to treatment occurred very rapidly. After stopping treatment in 8 out of these 12 episodes HE worsened again after 2 to 4 hours. The favourable clinical response was also documented by improvement of somatosensory evoked potentials. In 5 of the 8 episodes not reacting to flumazenil patients had signs of increased intracranial pressure. These findings indicate that flumazenil may be valuable in treatment of acute HE occurring in fulminant hepatic failure or in decompensated cirrhosis.