Several members of an inhibitor family of heterologous a-amylases and of trypsin have been isolated from wheat, barley and rye endosperms. Comparisons of the amino acid sequences of these inhibitors together with the chromosomal locations of their structural genes in the three species, indícate that they are encoded by a disperse multi-gene family that must have originated both by translocations and intrachromosomal duplications events that took place in common ancestors of wheat, barley and probably rye. Homology among some members of the inhibitor family and various proteins of maize, ragi, castor bean and others, indícate that this protein family extends to other phylogenetically distant species