Total nitrogen in developing wheat kernels was fractionated to give non-protein nitrogen and three protein fractions. Each fraction was hydrolyzed and analyzed for amide and arginine nitrogen.All fractions increased in amide and decreased in arginine nitrogen during kernel development. The main portion of the water-soluble protein is static in nature, and is considered to play no part in the metabolism of the endosperm proteins. The trend, with time, of amide in the two other protein fractions (soluble and insoluble in normal potassium iodide) was closely parallel to the trend of amide in non-protein nitrogen. The chemical nature of each of the gluten fractions in flour from the most insoluble to the most soluble is determined by the chemical nature of successive portions of the non-protein nitrogen in the wheat kernel at progressive stages of maturity.