With reference to a critical study of the relevant literature and to results from their own investigations, the authors emphasize the importance of the semi-essential and non-essential amino acids arginine, histidine, tyrosine, cystine and glutamic acid for the completion of essential amino-acid mixtures destined for parenteral feeding. MADDEN'S assumption that intravenously applied glutamic acid is intolerable was not supported by the authors' experiments in dogs. As evidenced by the increase of blood urea, the glutamic acid-containing amino-acid mixture was well utilizable. When glutamic acid is present, proline and alanine are obviously superfluous in amino-acid mixtures for parenteral feeding, since they are easily formed from glutamic acid by intermediary metabolism.