Amino acid levels were measured in the plasma and ascitic fluid of 13 alcoholic patients with liver cirrhosis and of 14 normal controls. The plasma aromatic amino acids of the alcoholic patients were not statistically different from those of the control subjects, whereas the levels of branched-chain amino acids were reduced (P less than 0.05). The values for the ratio of the muscle/liver metabolized amino acids (valine + isoleucine + leucine)/(phenylalanine + tyrosine + methionine) were statistically lower in the cirrhotic patients both in plasma and ascitic fluid (P less than 0.05). The amino acid levels in the ascitic fluid of the cirrhotic patients were slightly lower than those in the plasma of the same patients and the values for the muscle/liver metabolized amino acid ratio were similar in plasma and ascitic fluid. Aspartic acid, glutamic acid and glycine levels were higher among the cirrhotic patients (P less than 0.05). Cirrhotic patients present an alteration in amino acid metabolism which creates a different amino acid pattern in both plasma and ascitic fluid. The significance of the proposed ratio and its possible relation to hepatic failure are discussed.