The glucose oxidase-peroxidase system for the enzymatic determination of glucose was investigated with respect to the instability of the enzyme reagent, the buffering capacity of the reaction milieu, and the stability and sensitivity of the final chromogen. An improved procedure was developed in which the enzyme solution is both stabilized and more adequately buffered by reconstitution in 40% aqueous glycerol containing 0.04 M phosphate buffer, pH 7.0. The sensitivity and stability of the colored product is markedly increased when a final sulfuric acid concentration of 4.9 N is used.