OBJECTIVES: In a multinational, multicenter, observational study (PRESENT), patients treated with human premix insulin (with or without conventional oral medication) were converted to biphasic insulin aspart 30 (BIAsp 30) whilst maintaining their existing oral therapy. A sub-analysis (involving 1219 patients) demonstrated an improvement six months after therapy conversion of 1.66%-point in HbA1c and a reduced rate of hypoglycemic events (1079.8 to 290.2 per 100 patient years). METHODS: The published and validated CORE Diabetes Model was used to make long-term projections of clinical and cost outcomes based on patient characteristics (mean age 56.8 years, duration of diabetes 10.2 years, HbA1c 9.1%, BMI 28.7 kg.m-2) and treatment effects from PRESENT. Spanish mortality rates, baseline complications and costs of treating complications were derived from published sources. Transition probabilities were based on data from landmark clinical and epidemiological studies. Total direct costs (complications + treatment costs) were projected over patient lifetimes from a Spanish healthcare payer's perspective with future costs and clinical benefits discounted at 3.5% annually. RESULTS: Long-term projections indicated that BIAsp 30 treatment was associated with an improvement in discounted life expectancy of 0.77 years (11.33±0.15 versus 10.57±0.14 years). Taking quality of life into account led to a projected improvement of 1.03 quality-adjusted life years (QALYs) with BIAsp 30 over human premix insulin (7.83±0.11 versus 6.80±0.09 QALYs). Superior glycemic control associated with BIAsp 30 treatment was also projected to lead to fewer diabetes-related complications and a net reduction in total direct medical costs of €8339 (€32,107±1030 versus €40,446±1247). CONCLUSION: Higher pharmacy costs associated with BIAsp 30 treatment were offset by savings in the costs associated with diabetes-related complications versus human premix insulin. This resulted in a dominant scenario, where BIAsp 30 was associated with improved clinical outcomes and reduced costs compared to human premix insulin in the Spanish setting.