Seventy-two type II diabetic subjects were given Konjac food for 65 days. The data analyzed by multiple F test indicate that the fasting blood glucose (FBG) and the 2-h postprandial blood glucose (PBG) on the 30th and the 65th days after the food was ingested were significantly reduced (P = 0.001, P less than 0.001, respectively), as was the glycosylated hemoglobin level at the end of the trial (P less than 0.05). The final FBG and PBG of the subjects with initial FBG-O greater than 200 mg% decreased on the average by 51.8 and 84.6 mg%, respectively; those with FBG-O 150-200 mg% decreased by 24.1 and 68.7 mg%; and those with FBG-O less than 150 mg% decreased by 4.8 and 21.4 mg%. No significant changes in blood lipid indexes were observed, except that the triglyceride values of subjects with hypertriglyceridemia (greater than 200 mg%) significantly decreased by 118.7 mg%. It was concluded that Konjac food is very useful in the prevention and treatment of hyperglycemia.