Plasma amino acids profile is assumed to be a good index of whole body amino acids balance and in particular to give information on the actual control of the transplanted liver on protein metabolism. Variations in plasma amino acids profile were studied in 12 patients undergoing orthotopic liver transplantation. Total parenteral nutrition (TPN) was maintained at 26.05 +/- 1.53 kcal/kg and 0.117 +/- 0.01 gN/kg until the 7th postoperative day. Following this, an enteral nutrition (EN) was added as to maintain a mixed metabolic therapy at 30.28 +/- 2.76 kcal/kg and 0.198 +/- 0.01 gN/kg. Such a treatment completely satisfied the caloric needs, while nitrogen input was prudently kept low in accordance to the lack of data on the metabolic effectiveness of the transplanted liver. Amino acids profiles showed an early metabolic recovery of the new liver. Therefore nitrogen input could be higher and more adequate to nitrogen needs.