In order to investigate the changes of free amino acids during the differentiation and development of young spike in naked barley, a typical spring grain, Wanju, and two winter grains, Sedohadaka and Nonsankwa No. 1-6 differing in their spring habits, were analyzed at different growth stages by thin layer chromatography. In all the varieties 22 ninhydrin positive components were detected at the sowing time of March 5 and 20 components in the sowing plots of March 30. In case of the latter plot, β-alanine was identified only in both Wanju and Sedohadaka, whereas pipecolic acid was detected only in Nonsankwa No. 1-6. Particularly, it is interesting that β-alanine was observed only in the case showing the normal heading independent of the varieties and sowing times. Whether these components are directly related to the physiology of spring habits in barley or not is also a question to be answered. Of the major amino acids, alanine and γ-aminobutyric acid were always detected in appreciably large spots, and serine, leucine, aspartic acid, valine and asparagine were somewhat larger. In the plot of march 30, glutamic acid was also detected in very large spot in both Wanju and Sedohadaka at the stage of spikelet differentiation and in Nonsankwa No. 1-6 at the stage of bract differentiation. Histidine, which showed the only qualitative difference among the varieties during seed germination, cannot be observed at all. Proline observed considerably large spot during seed germination was always detected but very small except that it was observed in large spot at the stage of floret differentiation in Nonsankwa No. 1-6 in the plot of March 5.