In some circumstances, the premixed insulin should be switched to alternative therapy. The effectiveness and the safety of switching from premixed insulin to insulin glargine plus oral antidiabetic drugs (OADs) in Chinese patients with type 2 diabetes mellitus (T2DM) have not been clarified and, hence, will be assessed in this study. Chinese patients with T2DM (2013 men and women aged 18-75 years) who had received premixed insulin +/- OADs for >= 3 months with glycated hemoglobin (HbA1c) <= 10% were enrolled in a prospective, observational study conducted at 53 hospitals across China. At baseline and at the discretion of the physician, patients switched from premixed insulin to insulin glargine plus OADs. Changes in HbA1c, fasting plasma glucose (FPG), 2-hour postprandial glucose (PPG), treatment satisfaction, and the incidence of hypoglycemia were assessed for 16 weeks. In total, 1850 patients completed the study. Mean HbA1c level for the group decreased significantly (from 7.8% +/- 1.2% at week 1 to 7.0% +/- 1.0% at week 16; P < .0001), and 55.2% of patients achieved HbA1c < 7% at week 16. Mean FPG and 2-hour PPG decreased significantly (-1.4 +/- 2.2 and -2.1 +/- 3.9 mmol/L, respectively; both P < .0001), whereas patient satisfaction improved significantly. Adverse events were reported in 18.7% of patients. Chinese patients with T2DM who switched from premixed insulin to insulin glargine plus OADs achieved significantly improved glycemic control and treatment satisfaction with a low incidence of hypoglycemia. Patients who are most likely to achieve the HbA1c target less than 7% are younger, have shorter disease duration, and have lower baseline HbA1c and FPG levels.