The study was designed to investigate the antihyperglycemic effect of biochanin A on streptozotocin-diabetic rats. Diabetes was induced in adult male albino rats of the Wistar strain, weighing 180-200 g, by administration of streptozotocin (40 mg/kg of body weight) intraperitoneally. Diabetic rats showed increase in plasma glucose and glycosylated hemoglobin and a decrease in plasma insulin and hemoglobin. Activities of gluconeogenic enzymes such as glucose 6-phosphatase, fructose 1,6-bisphosphatase increased and glucokinase, glucose 6-phosphate dehydrogenase decreased in the liver of diabetic rats along with glycogen. Oral administration of biochanin A (10mg/kg body weight) or glibenclamide (600 μg/kg body weight) in 0.5% dimethyl sulfoxide, for 45 days, prevented the above changes and improved towards normality. In addition, protection against body weight loss of diabetic animals by biochanin A was also observed. No significant effect was observed in normal rats treated with biochanin A (10mg/kg bodyweight). These results showed that biochanin A has potential antihyperglycemic activity at a dose of 10mg/kg bodyweight in streptozotocin induced diabetic rats.