In both alcoholics and cirrhotics, we found a significant increase of plasma-aromatic amino acid and methionine levels, whereas glutathione was significantly reduced. The erythrocytes of these patients showed a significant increase of cysteine, glutamic acid, and glycine; gamma-glutamylcysteine was normal; and glutathione and other free amino acids were significantly decreased. Data suggest that, independent of liver cirrhosis, ethanol abuse affects the metabolism of amino acids and glutathione in both the plasma and the erythrocytes.