There appears to be a temporarily increased (three-to eightfold) amino-aciduria in kwashiorkor, which is rapidly reduced with treatment. This increased excretion was apparent when the data were expressed as a function of body weight or excretion of creatinine, as a percentage of intake or as amino-acid index. Further, this increase is due to the increased output of 17 amino acids rather than any single acid. Secondly, there is a grossly increased amino-aciduria in both normal infants and infants with kwashiorkor fed two synthetic amino-acid formulae, theoretically adequate: this appears to be due to a large extent to those acids present in the formula as the DL-isomers, although excretion of D-acids was also higher in the patients with kwashiorkor than in controls.