Burn injury induces time-dependent variations in plasma amino acids, ie, an initial hyperaminoacidemia reflecting proteolysis in the wound areas, a decrease in gluconeogenic amino acids a consequence of excessive utilization in the liver, and a progressive return to normal. There is also a durable hyperphenylalaninemia, reflecting increased protein turnover and specific alterations of sulfur amino acids. In burned rats, the same general pattern is observed, except that glycine rather than alanine and glutamine exhibits the largest variations. Improvements in nutritional support with regard to the amino acid composition of diets are envisaged.