The anti-diabetic effects of the methanol extracts of Cortex, Ramulus and Folium part of Eucommia ulmoides Oliver were investigated by the experimental diabetic model in rats. The increased blood glucose level in the diabetic rats induced by alloxan and streptozotocin was significantly lowered and a marked increase in body weight was shown with the treatments of the extracts of Cortex and Folium. The blood insulin level lowered by streptozotocin pretreatment was significantly recovered with the treatment of the extract of Folium. In glucose tolerance test, the extracts of Cortex and Folium displayed a significant inhibitory effect on the glucose level. The extracts of Cortex and Folium also caused a marked inhibition in increased blood pressure in the diabetic rats induced by alloxan.