Preliminary tests have shown that the endosperms of maize seeds homozygous for the opaque-2 mutant gene have a higher lysine content than normal kernels. As a critical test, a backcross progeny was divided into opaque-2 and normal kernels, the endosperms separated, and the amino acids determined. The opaque-2 endosperms had a different amino acid pattern and 69 percent more lysine than the normal seeds. The major reason for these changes is the synthesis of proteins with a greater content of basic amino acids in the acid-soluble fraction of the mutant endosperm. This is accompanied by a reduction in the ratio of zein to glutelin.