The plasma amino acid concentrations of cafeteria-fed and standard-fed rats gavaged either an essential amino acid mixture or saline solution have been studied from 14 to 30 days after birth. The consumption of a cafeteria diet caused higher levels in many amino acids. The amino acid-gavaged cafeteria-fed rats showed the highest cysteine levels. The amino acid gavage produced lower concentrations of alanine, glutamate+glutamine, hydroxyproline, proline and ornithine, in both cafeteria-fed and standard-fed animals. The results show that the supply of amino acids has a positive effect on nitrogen retention and amino acid availability in cafeteria-fed pups.