OBJECTIVE To study the effects of ethinyl estradiol on glucose metabolism in postmenopausal women. METHODS Postmenopausal women were randomized as nine cases (group A) receiving 0.025 mg ethinyl estradiol (EE) and ten cases (group B) receiving EE 0.05 mg for three months. The oral glucose tolerance test (OGTT) and frequently sampled intravenous glucose tolerance test (FSIGT) were performed before and after EE respectively. The levels of plasma glucose, insulin were measured and the area under curve (AUC) and insulin sensitivity indexes (SI) were calculated. RESULTS Both two dosages of EE administration effectively decreased the levels of fasting plasma glucose and insulin and significantly reduced the AUC of insulin. SI was increased significantly. There were no significant differences in AUC of glucose before and after treatment in group A, but in group B the AUC of glucose significantly increased after treatment. CONCLUSIONS EE may significantly reduce the levels of fasting plasma glucose and insulin concentrations and abate the insulin resistance in postmenopausal women; 0.05 mg EE possibly causes the deterioration in glucose tolerance, suggesting the use of 0.025 mg EE as an appropriate dosage.