The hypoglycemic effect of fractions of methanol extract of Cassia tora was investigated in diabetic rats. Sprague-Dawley male rats weighing 180∼230 g were divided into 6 groups. Diabetes was induced in the male rats by intravenous injection of streptozotocin at a dose of 45 mg/kg dissolved in citrate buffer (pH 4.5). The diabetic animals then had plasma glucose concentration of above 300 mg/㎗. Fractions of methanol extract of Cassia tora were administered orally into the diabetic rats for 14 days after streptozotocin injection. The food intake and body weight gain were monitored and plasma levels of glucose, triglyceride, free fatty acid, HDL-cholesterol, cholesterol and ALT activity were determined. Levels of glycogen, cholesterol and triglyceride in liver were analysed. Weights of liver and kidney were lighter in all the fraction-administered groups than streptozotocin-control group. Plasma glucose level was significantly decreased by the administration of butanol fraction at 14 days. Plasma triglyceride levels were lower in chloroform, butanol and H$_2$O fraction-administered groups compared to streptozotocin-control group. Plasma cholesterol and HDL-cholesterol levels were not significantly different in all groups. Administrations of each of the four fractions have decreased plasma free fatty acid level, ALT activity and liver triglyceride levels in the diabetic rats. Liver glycogen levels in chloroform, butanol and H$_2$O fraction-administered groups were higher than streptozotocin-control group. It is suggested from the results that butanol fraction of methanol extract of Cassia tora may contain the antihyperglycemic compounds.