Effect of isatin and of three its derivatives on content of lactate, pyruvate and glycogen was studied in rat tissues. The substances studied, except of 5-butylisatin, decreased the content of lactic acid with simultaneous increase of glycogen content in liver tissue under normal conditions. The pyruvate content was most markedly altered in presence of 5-bromoisatin and 5-butylisatin. In deficiency of oxygen a distinct increase in content of lactate and pyruvate was noted in animal tissues after the 5-bromoisatin preadministration. Under conditions of oxygen deficiency the substances studied were of distinct significance for more economical utilization of glycogen in liver tissue and skeletal muscles.