In order to examine the effect of amino-acid mixture for intravenous injection.(Vuj-N-type), the excretion of total nitrogen as well as the excretion of individual amino acids in urine were measured after intravenous administration to the subjects who were taking various amounts of dietary protein, i.e.standard period (1.34 g/Kg protein) low protein period (0.53-0.78 g/Kg) and recovery period (1.34g/Kg protein).The results obtained were as follows. 1) The percentage increase of urinary nitrogen due to amino-acid injection was 40-70% during the standard period, while it was 44-73% after three months of low protein diet and 45-110% in the recovery period.The percentage increase of total amino-acid excretion was 4.4%, 2.3% and 3.0% in these three periods respectiviely. Thus the amino-acid infused seemed to be utilized more effectively in the period of low protein. 2) The excretion rate of injected glycine was the highest among those of other amino-acids, and the lowest were those of phenylalanine and valine including leucine and isoleucine.The increase of utility of infused amino-acid in protein deficiency seemed to be the same among lysine, threonine, glycine, and valine (including leucine and isoleucine), while that of phenylalanine was somewhat less as compared with those of others.