The anti-diabetic effect of Cinnamomi cassiae extract (Cinnamon bark: Lauraceae) in a type II diabetic animal model (C57BIKsj db/db) was studied. Cinnamon extract was administered at different dosages (50, 100, 150 and 200 mg/kg) for 6 weeks. It was found that blood glucose concentration is significantly decreased in a dose-dependent manner (P<0.001) with the most in the 200 mg/kg group compared with the control. In addition, serum insulin levels and HDL-cholesterol levels were significantly higher (P<0.01) and the concentration of triglyceride, total cholesterol and intestinal alpha-glycosidase activity were significantly lower after 6 weeks of the administration. These results suggest that cinnamon extract has a regulatory role in blood glucose level and lipids and it may also exert a blood glucose-suppressing effect by improving insulin sensitivity or slowing absorption of carbohydrates in the small intestine.