Introduction: Mosapride, a benzamide derivative, is widely used in patients with motility disorders as a prokinetic agent. Recent studies suggested that mosapride may modulate the secretion and/or action of insulin through 5HT receptors. So we investigated the potential effect of mosapride on insulin sensitivity in subjects with impaired glucose tolerance, having high risks for Type 2 diabetes mellitus. Methods: Thirty subjects were selected for this study with informed consent (20:mosapride group, 10: placebo control group). Insulin sensitivity was measured by euglycemic Hyperinsulinemic clamp, before and after two weeks of mosapride administration. Results: No difference was found between the two groups in terms of sex, age, BMI, blood pressure, total cholesterol, triglyceride and HDL-cholesterol. After 2 weeks treatment of mosapride, fasting plasma glucose levels and insulin levels were decreased. Follow-up glucose disposal rates were higher than the Initial values, and were comparable to those of control subjects. Conclusion: Mosapride improved insulin action in pre-diabetic subjects and it can be regarded as a supplementary insulin sensitizer.