OBJECTIVE: This study was performed to evaluate whether an additional dose of NPH insulin at lunchtime might overcome the deleterious effects of waning basal insulinemia on pre-dinner and evening glucose values during insulin lispro intensive therapy with once daily basal insulin at night. RESEARCH DESIGN AND METHODS: The study was a 10-month multicenter, randomized, crossover trial. After a 2-month run-in period, subjects injected NPH insulin once (1 x NPH) or twice (2 x NPH) daily for 4 months in a randomized order. Adult patients were included if they had HbA(1c) levels <8.5%. Efficacy measures were HbA(1c) levels, 8-point glucose profiles, and the frequency of hypoglycemia. The statistical analysis included a within-patient comparison for crossover trials. RESULTS: In all, 104 patients completed the trial. The mean HbA(1c) level before randomization was 7.1 +/- 0.85%. The HbA(1c) levels did not change significantly within patients (t test, mean difference = 0.06%; 95% confidence interval [CI] -0.073 to 0.20). The pre-dinner blood glucose values were significantly lower during the 2 x NPH daily protocol, with a mean difference of 0.76 mmol/l (t test, P = 0.004; CI 0.25 to 1.3). In the evening, the frequency of hypoglycemia increased significantly during the 2 x NPH daily protocol with a median difference of 0.56 mild episodes/30 days (P = 0.001) and 6.9 severe episodes/patient year (P = 0.007), respectively. CONCLUSIONS: Equal HbA(1c) levels and increasing frequencies of hypoglycemia in the evening overshadow the slight improvement of the evening glucose profiles during a regimen with 2 x NPH daily insulin. Therefore, generalized use of a second injection of NPH insulin at lunchtime cannot be recommended to all adult patients with type 1 diabetes using intensive insulin lispro therapy.