In order to confirm that carbohydrate would not be a primary requirement for energy source in carp, from a view point of intermediate metabolism of glucose, incorporation of glucose-6-14C into glycogen and blood glucose, its excretion to 14CO2 and randomization of 14C in glucose molecule in carp which were fed the various diets consisting of carbohydrate and protein were investigated. Glucose-6-14C was scarcely incorporated into glycogen in all groups but oxidized to 14C02. When more than 50% of protein was contained in diet, oxidation of glucose-6-14C decreased remarkably, and at the same time blood glucose pool and the extent of randomi-zation of 14C in glucose were increased. From these observations it was suggested that carp possesses the active and reversible Embden-Meyerhof pathway but that glycogen is not a principal storage depot of energy.