Using the chromatographic analysis with Dowex 50 according to Stein and Moore the ninhydrin positive substances of plasma filtrates were determined before and sometimes after hydrolysis. Plasma filtrates of two normal adults, four normal children of different ages, two children with scurvy and three patients with some form of rickets were analyzed in whole or in part. It was shown, that most of the common amino-acids are present in notable amounts, while hydroxy-proline is lacking. Many unknown substances are also present, some of them seem to be inherent to age. Aspartic and glutamic acids are present in large amounts as asparagine and glutamine, while after hydrolysis only alanine, valine, leucine, phenyl-alanine, histidine and perhaps threonine and serine have been increased in concentration. The chromatographic studies of the plasma of children with scurvy and with rickets showed no significant differences as compared with controls.