Taurine (2-aminoethanesulfonic acid) has been shown to be a potent hypoglycemic agent in the Wistar Kyoto rat (WKY). Glucose and insulin levels were measured in serum at various times after glucose loading (400 mg/kg, i.p.). Pretreatment with taurine (200 mg/kg, i.p.) attenuated the rise in serum glucose levels at 0.5 hr after glucose administration. In addition, taurine also prevented the rise in serum immunoreactive insulin levels. The taurine analogue hypotaurine produced a similar inhibition in the rise of both serum glucose and insulin levels while beta-alanine, the carboxylic acid derivative of taurine, was totally ineffective. The enhanced glucose clearance can be explained by an increase in deoxyglucose accumulation in skeletal muscle and liver. In the liver, a 50% increase in glycogen synthesis was observed. A possible interrelationship between taurine and insulin receptor is discussed.