Abstract Two experiments were conducted to investigate whether values obtained using the true metabolizable energy (TME) assay are applicable in the formulation of practical diets for poultry. In the first study, five diets of increasing energy and nutrient density were assayed for TME and nitrogen corrected, apparent metabolizable energy. (AMEn). Chick response to each diet was evaluated in a 3-week growth trial. The determined TME of three practical diets exceeded the respective determined AMEn by 13 to 14%. A comparison between feed efficiency of chicks and the TME and AMEn content of the test diets indicated that TME values more closely reflected observed chick performance than did AMEn. In the second study, seven feed ingredients were assayed for TME and crude protein content. On the basis of these analyses, four isocaloric, isonitrogenous diets were prepared using the assayed lots of ingredients in varying proportions. In all diets, critical nutrients were included in excess of requirements, energy thus being limiting for optimal chick performance. In a 3-week growth study, chicks receiving each of the test diets exhibited virtually identical body weight gains and feed conversion ratios. Assays of the mixed diets indicated TME values of individual ingredients to be additive to within 1.6% of calculated totals. It was concluded that the TME system provided an accurate measure of metabolizable energy.