Introduction: This subgroup analysis of data from the 16-week Lantus Registry Study in China investigated the characteristics of patients with type 2 diabetes mellitus (T2DM) associated with clinical benefits of transitioning therapy from premixed insulin to insulin glargine (100 U/ml) plus oral antidiabetic drugs (OADs). Methods: The modified intention-to-treat population of the Lantus Registry Study, comprising 1847 patients with T2DM, were included in the current subgroup analyses. Enrolled patients were divided into subgroups based on efficacy variables of endpoint glycated hemoglobin (HbA(1c)), endpoint fasting plasma glucose (FPG), and change in HbA(1c) from baseline. The baseline characteristics of those who did and did not achieve HbA(1c) <7.0% were compared, as were those with improvement, no change, or deterioration in HbA(1c). Characteristics of patients who were unable to achieve HbA1c <7.0%, further grouped according to whether or not they achieved FPG <= 6.1 mmol/L, were also compared. Logistic regression analysis was used to identify factors associated with achieving HbA(1c) <7.0%. Results: Comparison between subgroups demonstrated that patients with endpoint HbA1c <7.0% were significantly younger, with a shorter duration of diabetes and lower baseline FPG, HbA(1c), body mass index, and dose of premixed insulin than patients with endpoint HbA(1c) >= 7.0%. Logistic regression analysis revealed a negative correlation between baseline age, HbA(1c), FPG, and duration of diabetes with achieving HbA(1c) <7.0%. When stratified according to change in HbA(1c), the improvement group was younger, with higher baseline HbA(1c) and a greater number of patients with duration of diabetes <= 5 years. Three-quarters of patients unable to achieve HbA(1c) <7.0% also failed to reach FPG <= 6.1 mmol/L. Conclusion: Younger patients with a shorter duration of diabetes and lower HbA(1c), FPG, and premixed insulin dose following a switch in treatment to insulin glargine (100 U/ml) plus OADs from premixed insulin have greater potential to achieve HbA(1c) <7.0%. Poorly controlled patients with higher baseline HbA(1c) are most likely to experience an improvement in HbA(1c) following the switch in therapy. The majority of patients unable to achieve HbA(1c) <7.0% also failed to reach FPG <= 6.1 mmol/L, highlighting the importance of adequate titration of insulin glargine to achieve adequate FPG control, which can enable achievement of target HbA(1c).