This volume contains the papers presented at the Inter- national Symposium on "Cirrhosis, Hepatic Encephalopathy and Ammonium Toxicity", held in Valencia, Spain, November 27-29, 1989. Hepatic cirrhosis as well as other liver failures usual- ly lead to hepatic encephalopathy which is an important cause of death in occidental countries. However the molecular bases of the pathogenesis of hepatic encephalopathy remain unclear and several hypotheses have been proposed. Hyperammonemia is considered one of the main factors responsible for the mediation of hepatic encephalopathy. Therefore, a part of the book is devoted to the effects of hyperammonemia on cerebral function, ammonia and amino acid metabolism, brain microtobules, astrocytes and synaptic trans- mission and their possible role in the pathogenesis of hepatic encephalopathy. Carnitine has a remarkable protective effect against acute ammonium intoxication. Thus some results regarding this effect are also presented, as well as the clinical use of car- nitine. The alterations of the metabolism of ammonia and of seda- tives in liver diseases and their clinical implications are also discussed. The possible role of altered GABA-ergic neurotransmission on the pathogenesis of hepatic encephalopathy has received considerable attention recently. Results of these studies and those on benzodiazepine receptor ligands are presented as well as those on the hypothesis of the role of altered synaptic plasma membrane on the pathogenesis of hepatic encephalopathy.