The effects of Trichosanthes kirilowii Max. subfractions, which has long been used as a wild vegetable and folk medicine, on insulin activity and acute toxicity were investigated. Diabetes melitus was induced in male Sprague-Dawley rats by the injection of streptozotocin(STZ) into the tail vein at a dose of 45mg/kg. The hexane fraction of the plant was subfractioned by silica gel column chromatography and were administered orally for 14 days and the normal and STZ-control group were orally administered with tween 80. The body weight gain was monitored and plasma levels of glucose, cholesterol, triglyceride, free fatty acid HDL-cholesterol were determined. The plasma activities of aspartate aminotransferase(AST) and alanine aminotransferase (ALT) were analysed. The subjraction A of hexane fraction lowered plasma glucose levels significantly and increased insulin activity compared to that of STZ-control. The activities of AST and ALT were decreased by administration of subfractions A and C of hexane fraction. The intakes of the hexane fraction of Trichosanthes kirilowii Max. did not showed the acute toxicity. It is suggested from the results that the subfraction A of the hexane fraction of Trichosanthes kirilowii Max. showed a hypoglycemic effect on diabetic rats and that the subfraction may be beneficial for insulin secreation.