The composition of an amino acid solution for intravenous use in newborns is discussed in the light of the metabolic kinetics of its constituents. Such a solution would be optimal when based on the transfer characteristics of the single amino acids used. Under these circumstances one would avoid imbalances in the respective blood levels. In particular, the average amount of such a solution needed, and the maximal turnover rates per hour of the specific amino acids during the first 4 weeks of life are discussed.