Objective: To investigate whether once daily biphasic insulin aspart 30 (BIAsp 30) is noninferior to once daily insulin glargine (IGlar) among Chinese and Japanese insulin-naive subjects with type 2 diabetes mellitus (T2DM). Research design and methods: This was a 24 week treat-to-target trial (NCT01123980) that included patients with T2DM who were poorly controlled on a combination of metformin and insulin secretagogue (or with a maximum of one more OAD) for 6 months. Patients were randomized to once daily BIAsp 30 or once daily IGlar and their secretagogue standardized to glimepiride 4 mg/day, metformin to 1500 or 2500 mg/day before randomization. Results: At Week 24, mean change from baseline in HbA1c was -0.78 +/- 0.88% (mean +/- SD) and -0.65 +/- 0.92% (-8.49 +/- 9.65 and -7.08 +/- 10.1 mmol/mol) for the BIAsp 30 (n=261) and IGlar (n=260) groups, respectively. The stimated between-group difference (BIAsp 30 vs IGlar) in HbA1c change was -0.12% (95% Cl: -0.25, 0.02) (-1.28 mmol/mol [95% Cl: -2.75, 0.19]), thus treatment with BIAsp 30 was noninferior to IGlar with respect to HbA1c (non-inferiority margin 0.4%). Although reduction in mean 9-point self-measured plasma glucose (SMPG) profile was comparable between the two groups, BIAsp 30 showed significantly lower PG levels at three time points post-dinner and a higher PG level before dinner compared to the IGlar group (all p<0.05). Comparable number of subjects reported hypoglycemic events (155 [59.4%] for BIAsp 30, 148 [56.9%] for IGlar). Conclusions: BIAsp 30 once daily showed similar HbA1c reduction and a similar safety profile to IGlar when used in insulin-naive Chinese and Japanese patients on metformin and a sulfonylurea. Moreover, it provided a better coverage of post-dinner glycemic control needs than those who received IGlar. The open-label design and insufficient insulin dose titration were the main limitations of the study.