BACKGROUND Data on switching from premixed insulin to a basal-bolus regimen in routine clinical practice are sparse. The aim was to evaluate the efficacy and safety of switching from twice-daily premixed insulin to basal glargine plus rapid-acting insulin in a "real-world" clinical practice setting in Belgium and The Netherlands. METHODS This prospective, 6-month, noninterventional, observational study was conducted in 37 centres in Belgium and 19 centres in The Netherlands. Adults (> or =18 years of age) with type 2 diabetes were eligible if they were not taking oral antihyperglycaemic drugs or only taking metformin. The primary objective was the proportion of patients attaining glycated haemoglobin (HbA1c) <7% at months 3 and 6. Secondary objectives included changes in HbA1c, weight, body mass index (BMI), insulin doses, hypoglycaemic events, and treatment satisfaction. RESULTS There were 214 patients from Belgium and The Netherlands enrolled. Mean age was 64.6 years, weight was 89.5 kg, BMI was 31.4 kg/m2, and duration of diabetes was 12.1 years. At month 6, the percentage of patients with HbA1c <7% increased from 3.3% to 24.9% (p<0.001). Mean HbA1c at baseline was 8.9%; mean change from baseline was -1.5% (p<0.001). Glargine and prandial insulin doses increased (p<0.001, each), while body weight and BMI were unchanged. Hypoglycaemic events did not increase. Overall treatment satisfaction improved significantly (p<0.001). CONCLUSIONS In a Belgian and Dutch clinical practice setting, patients with type 2 diabetes that is poorly controlled on premixed insulin experienced significant improvements in glycaemic control, without a concomitant increase in hypoglycaemic events or weight, when switched from premixed insulin to basal-bolus glargine plus rapid-acting insulin. As a result, treatment satisfaction significantly improved.