Technical Abstract: Molecular weight distribution (MWD) of proteins extracted from hard spring wheat grain was analyzed by size exclusion HPLC to investigate associations with wheat and breadmaking quality characteristics. Certain protein fractions were found to be related to associations between wheat and breadmaking parameters specifically when effect of quantitative variation of protein on those parameters was statistically eliminated by partial correlation analysis. SDS unextractable high molecular weight polymeric proteins had positive partial correlations with percent vitreous kernel content and breadmaking parameters, including mix time and bread loaf volume. SDS extractable protein fractions that were eluted before the primary gliadin peak had positive partial correlations with kernel hardness and water absorption parameters. Proportion of main gliadin fractions in total protein had a negative partial correlation with bread loaf volume and positive correlations with kernel hardness and water absorption parameters. Intra-sample uniformity in protein MWD and kernel characteristics was estimated from three kernel subsamples which were separated according to single kernel protein content within individual wheat samples by a single-kernel near-infrared sorter. Wheat subsamples were significantly different in protein MWD. Intra-sample uniformity in protein MWD did not differ greatly among wheat samples.