A single administration of taurine at a dose of 200 mg per kg of body weight increased the insulin-like activity in blood plasma, elevated two-fold the content of glycogen in liver tissue, decreased content of sugars in blood. In vitro taurine increased the consumption of glucose by isolated diaphragm and increased the insulin activity. The adenilate cyclase activity was increased in incubation mixture, containing the diaphragms and taurine added. The data obtained and the recognized insulin-like effect of 3',5'-AMP and theophylline suggest that the insulin-like action of taurine is mediated through the cyclic 3',5'-AMP.