Experiments were conducted to determine the chromosomal location of the gene conditioning overproduction of a methionine-rich, 10-K zein in maize kernels of line BSSS53. In addition, the chromosomal location of the structural gene encoding the overproduced protein was determined. Whereas the structural gene, designated Zps10/(22), was found to be located on the long arm of chromosome 9 near the centromere, the locus regulating overproduction of the zein protein was mapped to the short arm of chromosome 4. This regulatory gene has been designated Zpr10/(22). Regulation of 10-K zein production by Zpr10/(22) is, therefore, via a trans-acting mechanism.