High-molecular-weight glutenin subunits (HMW-GS), one class of seed storage proteins, are important determinants of the bread-making quality of wheat flour. To change the amount and composition of these proteins via genetic engineering, a gene encoding a novel hybrid subunit under the control of native HMW-GS regulatory sequences was inserted into wheat. Of 26 independent transgenic lines identified by bialaphos selection, 18 expressed the cotransformed hybrid HMW-GS gene in their seed. The hybrid subunit accumulated to levels comparable to those of the native HMW-GS. These results show that a native HMW-GS gene promoter can be used to obtain high levels of expression of seed storage and, potentially, other proteins in transgenic wheat endosperm. Transgene expression was stable for at least three seed generations in the majority of lines. These experiments demonstrate the feasibility of constructing wheat plants with novel seed protein compositions.