SummaryGluconic acid was found to make up about 25 % of the total water-soluble acid content of both royal jelly and worker jelly. When freshly collected royal jelly was kept at 35°C, there was an increase in its acidity, an uptake of oxygen, and an evolution of hydrogen peroxide. It is concluded that part of the gluconate is producedin vitroby a glucose oxidase system secreted by the hypopharyngeal glands of the nurse bees.