This study investigated the non-inferiority of mitiglinide 10 - 20 mg versus nateglinide 120 mg, given orally three times daily for 20 weeks, in 291 Chinese type 2 diabetes mellitus (DM) patients in whom adequate blood glucose control had not been achieved by diet and exercise. Mitiglinide was started at 10 mg three times daily for 12 weeks and thereafter could be increased to 20 mg three times daily, depending on symptoms. In the mitiglinide and nateglinide groups the change in glycosylated haemoglobin (HbA(1c)) from baseline to week 12 was -0.53 +/- 1.08% and -0.58 +/- 1.04%, respectively, and further decreased by -0.77 +/- 1.06% and -0.71 +/- 1.12%, respectively, at week 20 compared with baseline. The intergroup difference (95% confidence interval) of HbA(1c) was 0.05% (-0.19, 0.30) at week 12 and 0.06% (-0.31, 0.19) at week 20. Similar changes in HbA(1c) were seen in patients whose baseline value was < 8.0% as well as in those aged >or= 60 years. Comparable reductions in other blood glucose variables were noted in the two groups. Adverse events in the mitiglinide and nateglinide groups were noted in 54.5% and 57.9% of patients, respectively. In conclusion, mitiglinide 10 - 20 mg three times daily provided similar blood glucose control to nateglinide 120 mg three times daily in type 2 DM patients, including the elderly and patients with mild diabetes mellitus.