The apparent and true metabolizable energy concentrations of 22 cultivars of sorghum grains, differing in their tannic ac id content, were determined by feeding samples of the different varieties to adult roosters. A highly significant negative correlation was found to exist between the M.E. of the grain and its tannic acid content, this relationship being due to a decreased digestibility with increasing tannic acid concentration. This finding is discussed in relation to the possible causes of such reduced digestibility, means by which the adverse effects of tannic acid can be reduced, and the importance of determining the tannic acid content of sorghum grains destined to be fed to non-ruminants.