Multiple daily insulin injection (MDI) programs are commonly accompanied by considerable glycemic variation and hypoglycemia. In order to determine whether use of insulin glargine as a basal insulin would result in comparable HbA1c with less glycemic variation and hypoglycemia than ultralente insulin, 22 individuals with type 1 diabetes, experienced with MDI, and a HbA1c of <7.8 % were randomized, to receive either glargine or ultralente as the basal insulin for 4-months. Aspart insulin was used as the prandial. Physicians providing insulin dose adjustment advice were masked to the type of basal insulin. Treatment with glargine resulted in lower mean HbA1c, less nocturnal variability , and less hypoglycemia primarily due to less daytime hypoglycemia (p=0.002). On the other hand, serious hypoglycemia and average glucose concentration measured with continuous glucose monitoring system (CGMS) did not differ. We conclude that, while use of either ultralente or glargine as a basal insulin can result in excellent glycemic control, treatment with glargine is associated with slightly but significantly lower HbA1C, with less nocturnal glycemic variability and less hypoglycemia.