OBJECTIVES: Treating patients to target has been shown to delay complications of type 2 diabetes mellitus (T2DM). We developed a model to explore the effectiveness of oral agents in achieving target levels for HbA1c and lipids in patients with T2DM. METHODS: The model is broad enough to cover most relevant comparisons. One analysis considered patients with T2DM and moderate dyslipidaemia: Triglycerides (TG) of 2.66 +/- 1.77 mmol/l and High Density Lipoprotein Cholesterol (HDL-C) of 1.09 +/- 0.26 mmol/l, who had failed metformin/sulphonylurea therapy. Following UK guidelines, patients either received rosiglitazone plus a sulphonylurea (Rosi+SU) or a hypothetical treatment that would simultaneously improve HDL, TG and HbA1c by 10%. Patients switched to insulin if therapy was not tolerated or HbA1c targets not met. The main outcome measure was Days at Target, defined as the number of days on which American Diabetic Association target levels for HbA1c, TG and HDL-C were achieved. The time horizon considered was 3 years, composed of six month cycles: long-term diabetic complications were not included. RESULTS: For Rosi+SU over one year, a cohort of 100 patients would spend 27,854 patient-days at HbA1c target, but only 5,808 patient-days at combined HbA1c and lipid targets. The increase in Days at Target per 100 patients treated was 136 for a 10% improvement in TG; 192 for a 10% improvement in HDL; 228 for a 10% improvement in HbA1c, and 667 for improvement in all three. The model was sensitive to the severity of dyslipidaemia at baseline. CONCLUSION: The model suggests that existing agents are more effective at achieving HbA1c control than reaching target lipid levels. Improving HbA1c would provide the single largest gain in Days at Target, but simultaneous improvement in HbA1c and lipids would be needed to achieve a substantial gain in diabetes control.