The keeping properties of different flours varied considerably. Aging was accompanied by increased absorption regardless of whether the flour deteriorated in baking quality. Increased acidity developed in all flours, but was not a good measure of deterioration. Storage in sealed containers favored acidity increases, while storage in sacks favored deterioration. A decrease in ether extract accompanied deterioration, while decrease in the less soluble lipoids appeared to take place in all samples.The changes in physical properties of gluten gave the best indication of deterioration. Gluten from deteriorated flour was harsh, spongy and short, and could not be completely dispersed in sodium salicylate. Unsaturated fatty acids added to flour had the same effects on gluten, but not on baking quality. Ground wheat germ added to deteriorated flour improved the gluten and restored its solubility. The more insoluble germ lipoids were the effective substances. Alcohol extraction of flour caused deterioration, but gluten quality was largely restored by addition of germ. All results indicate the lipoids are adsorbed on the protein of gluten.It is concluded that the unique physical properties of gluten are to a considerable extent dependent on the relatively insoluble lipoids present. The possibility of gluten denaturation being a breakdown of the protein-lipoid complex is discussed.