Renown wheat, OAC 21 barley, and Vanguard oats were grown in test plots, and the plants and their parts analyzed at approximately weekly intervals for thiamine and riboflavin. In wheat and barley, thiamine increased till after heading, translocation of it to the kernel continuing till the time of ripening. The thiamine content of the oat plant and its kernels continued to increase to the 'dead ripe' stage. When ripe, from 80 to 90% of the total thiamine in the tiller was located in the kernels, with the rest in the stem and, in barley, in the glumes and rachis. Negligible amounts were found in the leaves of all three varieties and in the glumes and rachis of wheat and oats. The riboflavin content of wheat decreased continuously till the plant ripened, when it became constant. The amount in the kernels was also constant at this stage. There were initial increases in both barley and oats, after which the amounts decreased till the grains were ripe. Barley kernels showed a constant riboflavin content from just before this stage. The riboflavin content of oat kernels continued to rise even after the grain was ripe. Less than half of the riboflavin of the ripened plants was found in the kernels. The stem contained nearly as much—in the case of wheat, more—while appreciable amounts occurred in the leaves.