OBJECTIVES: To project comparative economic and clinical outcomes associated with treating type 1 diabetes patients on basal-bolus therapy with insulin glargine (IGlar) or detemir (IDet), each combined with aspart (IAsp). METHODS: A published, peer-reviewed and validated computer simulation model of diabetes was used to project clinical and cost outcomes over time horizons of 5, 10, 20, and 35 years. Treatment effect data were derived from a multicenter, 26 week randomized controlled trial among subjects with a mean age of 40.2 years and baseline HbA1c of 8.84% (duration of diabetes: 16.7 years). Equivalent reduction of HbA1c, the primary endpoint, was observed (NS) and minor hypoglycemia was parallel (NS), though statistically significant improvements in nocturnal (32% lower; p=0.046) and major hypoglycemic episodes (72% lower, p=0.047; 6.51 vs. 24.5 events per 100 patient years) favored IDet. Costs were taken from published sources in the US and expressed in 2004 US dollars ($). Clinical and cost outcomes were discounted at 3% per annum. Sensitivity analyses on key input parameters were performed. RESULTS: Treatment with IDet was associated with improvements in life expectancy (0.002 to 0.08 years) and quality-adjusted life expectancy (0.01 to 0.06 QALYs). Direct medical costs from a US Medicare perspective (pharmacy plus complication costs) were lower in the IDet group ($672 to $5174), with the incremental value increasing as the time horizon lengthened. One-way sensitivity analysis on pharmacy costs (±15%), discount rate (0-6%), complication costs, and duration of treatment effect on HbA1c (<5 years) support the robustness of these findings. CONCLUSION: Clinical benefits associated with IDet+IAsp therapy compared to IGlar+IAsp were projected to improve life expectancy, quality-adjusted life expectancy and to reduce costs in patients with type 1 diabetes over a time horizon of 5 to 35 years.