The reason branched chain aminoacids are decreased and aromatic aminoacids increased in chronic liver failure is unclear. Branched chain aminoacids are mainly catabolised in muscles, and it is known that protein energy malnutrition may decrease the concentration of these aminoacids in plasma. In this study we have evaluated the nutritional status of a group of cirrhotics and compared it with their plasma aminoacid imbalance. Fourteen patients were considered as well-nourished and nine as malnourished. Plasma levels of branched chain aminoacids were significantly decreased and the phenylalanine increased in the malnourished group. Arm muscle circumference was significantly correlated with branched chain aminoacids. In conclusion our data suggest that malnutrition may contribute to the low levels of these aminoacids in patients with liver cirrhosis.