OBJECTIVE: To determine the safety and efficacy of the long-acting analog insulin glargine compared with NPH insulin in patients with type 2 diabetes who were previously treated with insulin alone. RESEARCH DESIGN AND METHODS: A total of 518 subjects with type 2 diabetes who were receiving NPH insulin with or without regular insulin for postprandial control were randomized to receive insulin glargine (HOE 901) once daily (n = 259) or NPH insulin once or twice daily in = 259) for 28 weeks in an open-label, multicenter trial. Doses were adjusted to obtain target fasting glucose <6.7 mmol/l. At study end point, the median total daily insulin dose in both treatment groups was 0.75 IU/kg. RESULTS: The treatment groups showed similar improvements in HbA1c from baseline to end point on intent-to-treat analysis. The mean change (means +/- SD) in HbA1c from baseline to end point was similar in the insulin glargine group (-0.41 +/- 0.1%) and the NPH group (-0.59 +/- 0.1%) after patients began with an average baseline HbA1c of approximately 8.5%. The treatments were associated with similar reductions in fasting glucose levels. Overall, mild symptomatic hypoglycemia was similar in insulin glargine subjects (61.4%) and NPH insulin subjects (66.%) However, nocturnal hypoglycemia in the insulin glargine group was reduced by 25% during the treatment period after the dose-titration phase(26.5 vs. 35.5%, P = 0.0136). Subjects in the insulin glargine group experienced less weight gain than those in the NPH group (0.4 vs. 1.4 kg, P < 0.0007). CONCLUSIONS: In patients with type 2 diabetes, once-daily bedtime insulin glargine is as effective as once- or twice-daily NPH in improving and maintaining glycemic control. In addition, insulin glargine deonstrates a lower risk of nocturnal hypoglycemia and less weight gain compared with NPH insulin.