The objective of this observational program was to evaluate the efficiency and safety of insulin glargine used to treat patients with type 2 diabetes mellitus (DM2) who failed to achieve adequate compensation of carbohydrate metabolism during therapy with NPC insulin in combination with oral hypoglycemic agents or prandial insulins. The secondary objective was to estimate satisfaction of physicians with the results of insulin glargine therapy. The open, prospective non-randomized multicentre observational study included 7.334 patients of the mean age 58.3±9.0 years presenting with type 2 diabetes mellitus and treated using a combination of NPC insulin and oral hypoglycemic agents or prandial insulins. The mean duration of the disease was 10.5±4.7 years, HbA1c level 9.6±1.7%, fasting blood glucose level 10.3±2.5 mmol/l. The total duration of the study was 6 months. After inclusion in the program, the patients were transferred from NPC insulin to insulin glargine with subsequent titration of the dose. The HbA1c level decreased from 9.6±1.7% to 8.0±1.2% and 7.2±1.0% within 3 and 6 months after the inclusion into the study respectively (p<0.001 for both values). The fasting blood glucose levels exhibited a similar trend. The target HbA1c level of ≤ 7% was achieved within 3 months in 29.2% of the patients and within 6 months in 53.8%. Simultaneously a reduction in the incidence of mild and severe hypoglycemic symptoms was documented both during the daytime and at night. The physicians described the results of the treatment as "good" and "very good" in 80.7% and 93.2% of the patients 3 and 6 months respectively after transfer from NPC insulin to insulin glargine in combination with oral hypoglycemic agents. It is concluded that substitution of NPC insulin by insulin glargine for the treatment of patients presenting with type 2 diabetes mellitus not only improves the quality of glycemic control but also significantly reduces the frequency of mild and severe hypoglycemic symptoms.