Abstract Four experiments were conducted using chicks to evaluate the protein quality of four corn gluten feed (CGF) samples (CGF1 through 4). In addition, a 48-h excreta-collection assay was conducted using cecectomized (CEC) and conventional (CONV) cockerels to determine amino acid digestibility and TMEn. The protein efficiency and net protein ratios, estimated from feeding chicks a N-free diet or diets containing 9% CP supplied solely by CGF, were significantly higher for CGF3 (2.9 and 3.3, respectively) relative to the other three CGF diets (χ = 2.2 and 2.7, respectively). The order of amino acid limitation in CGF was determined with a 14% CP, semipurified diet supplemented with various combinations of essential amino acids. The results indicated that Trp and Lys were equally first-limiting in CGF protein, with Arg being the third-limiting amino acid. Lysine bioavailability, determined by a chick growth assay, was 83, 63, 87, and 57% for CGF1 through 4, respectively. The values did not differ significantly among CGF sources, but the Lys bioavailability values for CGF2 and 4 were significantly lower man that for crystalline L-Lys·HCl (100%). Tryptophan bioavailability in one CGF from two chick growth assays averaged 68%. Lysine digestibility values for CEC birds used in the excreta-collection assay were 69, 60, 72, and 79%; Trp digestibility values were 80, 65, 80, and 86% for CGF1 through 4, respectively. Digestibility values from CEC birds were significantly lower than those from CONV birds for most of the amino acids in CGF2 but not the other CGF. The TMEn values for CEC birds averaged 7.5% lower than those for CONV birds, with the differences being significant for CGF2. The TMEn values measured in CONV birds were 3.179, 2.754, 2.776, and 2.785 kcal per g of DM for CGF1 through 4, respectively.