BACKGROUND: Mitiglinide, one of the meglitinides, is expected to prevent postprandial hyperglycemia of type 2 diabetes by enhancing early phase insulin secretion. The aim of this study was to verify the efficacy and safety of mitiglinide compared to nateglinide. METHODS: One hundred eleven of diabetic patients were randomised and administered of mitiglinide (n = 56) and nateglinide (n = 55) before a meal time for 12 weeks. The changes of HbA1c, fasting plasma glucose (FPG) and postprandial plasma glucose (PPG) were analyzed. The safety of this drug was investigated as well. RESULTS: The change of HbA1c was not significantly different between two groups (-0.77 +/- 1.08% in mitiglinide vs. -0.66 +/- 0.79% in nateglinide, P = 0.57). The reduction of FPG (-12.2 +/- 25.0 mg/dL vs. -6.1 +/- 22.3 mg/dL, P = 0.218), PPG 1 hr (-48.0 +/- 47.1 mg/dL, vs. -29.4 +/- 43.2 mg/dL, P = 0.051), and PPG 2 hr (-59.2 +/- 58.0 mg/dL vs. -43.3 +/- 59.0 mg/dL, P = 0.194) were not significantly different between the mitiglinide and the nateglinide, respectively. Drug-related adverse effects were not different between two groups (16.1% in mitiglinide vs. 27.8% in nateglinide, P = 0.137). The frequency of hypoglycemic events were not different between two groups (8.9% in mitiglinide vs. 14.8% in nateglinide, P = 0.339). There were two patients who had complained shoulder pain in the mitiglinide or deterioration of visual acuity in the nateglinide, but those were found to be unrelated with medications. CONCLUSION: This study showed that mitiglinide had reduced HbA1c as similar to nateglinide and that significantly improved HbA1c, FPG and PPG during 12 weeks of treatment. The safety of mitiglinide was also comparable to nateglinide. Mitiglinide could be used as an effective glucose-lowering agent by enhancing early insulin secretion and reducing postprandial glucose excursion, and thereby might contribute long-term cardioprotective effect in Korean type 2 diabetic patients.