In this study, 708 patients who had sub-optimal glycated hemoglobin levels while taking metformin and sulfonylurea were randomly assigned to receive biphasic insulin aspart twice daily, prandial insulin aspart three times daily or basal insulin detemir once daily. During the 3 year follow-up, the three different insulin regimens achieved similar median glycated haemoglobin levels but the distribution differed with fewer patients achieving glycemic targets in the biphasic group than either the prandial group or the basal group. Patients gained weight in all regimens but weight gain was highest in the prandial group. Thus, fewer hypoglycaemic episodes and less weight gain occurred in patients on basal insulin. Thus, these findings encourage the addition of insulin to oral antidiabetic therapy and its intensification in clinical practice.