Abstract Two mutant genes, Opaque-2 and Floury-2, have been shown to produce changes in the appearance and in the amino acid composition of corn endosperm (Mertz et al., 1964; Nelson et al., 1965). The superior nutritive value of Opaque-2 corn for the rat (Mertz, 1966) and pig (Cromwell et al., 1967) and the superior nutritive value of Floury-2 corn for the chick (Cromwell et al., 1968) have been demonstrated. These effects have been attributed to the altered amino acid composition of the mutant corns. It was considered desirable to compare the metabolizable energy values of these mutant corns with that of normal corn. PROCEDURE Two trials, each involving 112 two-week old Hubbard White Mountain male chicks randomly assigned to four experimental treatments, with seven birds assigned to each of four replications per treatment, were conducted to determine the metabolizable energy of normal, Opaque-2 and Floury-2 corns for the chick. The Opaque-2 . . .