The kinetics of wheat leaf invertase have been investigated as a basis for its quantitative estimation. No evidence was obtained which indicated that wheat leaf invertase consists of a phosphorylase and a phosphatase. Solid preparations of the enzyme may be made by precipitating the invertase with ammonium sulphate from wheat leaf juice which has been previously freed from chlorophyll by precipitation with acetate buffer at pH 4.5. A study of the distribution of this enzyme in the first leaf of wheat shows that the enzyme reaches its maximum concentration in the leaf just at the close of the period of elongation. The enzyme is more abundant in the basal part of the leaf than the tip and this condition is taken to indicate that the enzyme is associated with the vascular tissue (phloem or phloem parenchyma) rather than the chlorenchyma.