Technical Abstract: The development of high quality wheat (Triticum aestivum L.) cultivars depends on a thorough understanding of the genetic and environmental influences on the constituents of grain. Arabinoxylans are important albeit quantitatively minor constituents of wheat grain; they can interact with large weight ratios of water and participate in oxidative cross-linking and gel formation. In this study, 26 hard winter and 25 hard spring wheat genotypes from breeding programs in the U.S. Pacific Northwest were analyzed for water-soluble and total arabinoxylan content. Each genotype was grown in three environments. There were significant differences among water-soluble (WS-AX) and total (TO-AX) arabinoxylan contents (G, E, and G*E model R2s 0.64-0.96). WS-AX genotype mean content ranged about 2-fold (0.39 to 0.81% for winter, and 0.48 to 0.92% for spring genotypes). TO-AX genotype mean content ranged from 3.1 to 4.0% for winter and 3.9 to 4.7% for spring genotypes. Type III SS F-ratios for ‘genotype’ were highly significant (P<0.0001) for both AX fractions of both winter and spring genotypes. ‘Hollis’ spring wheat had the highest WS-AX content and ‘WQL9HALP’ spring wheat (a hard NIL to ‘Alpowa’) had the highest TO-AX content. Repeatability estimates were 0.71 and 0.89 for WS-AX, winter and spring; and 0.30 and 0.62 for TO-AX, winter and spring genotypes, respectively. These preliminary results indicate that there is sufficient repeatable genetic variation to improve wheat cultivars for AX contents.