In 12 experiments with S.C.W.L. roosters it was shown that for each of 12 feedingstuffs there was a linear relationship between feed input and the amount of energy voided as excreta. In the 24 h. period, following 21 hr. of starvation, roosters receiving no feed excreted 4.07 kcal./kg. of body weight. When dextrose was fed the energy voided as excreta did not increase with dextrose input; consequently, the true metabolizable energy (T.M.E.) value of dextrose is its gross energy value. The T.M.E. values were not affected by the level of feed input and appeared to be additive. A simple, rapid assay for T.M.E. was developed, based on gross energy assays of the test feed and of excreta voided over 24 hr. by roosters force fed the test feed and other starved over the same period.