OBJECTIVES To perform a comparative study comparing annual costs linked to the treatment with Insulin Glargine (IG) and Insulin Detemir (ID) from the Mexican private market perspective. METHODS Clinical data related to each treatment derives, from a study performed by Rosenstock et.al (2006): a 52-week open-label, parallel, multinational trial, which compares efficacy and safety of IG and ID. This trial demonstrated no difference in terms of HbA1c and tolerability. However, this study has shown that patients treated with IG required a lower total dose of insulin, and that 55% of patients treated ended up the study with two injections per day in order to reach control. The cost of each insulin regimen was calculating using the unit cost of insulins, needles and blood glucose tests. Costs calculations referred to year 2008 and unit costs were derived from public tenders databases and published tariffs. A sensitivity analysis was performed using a Monte Carlo simulation. RESULTS Overall, patients treated with ID required 59% more insulin than those treated with IG. In patients with DM2, management with IG has lower total costs than IG, which allows savings of US$474.7 per patient-year. Savings were related to the costs of total insulin, needles and blood glucose tests. Sensitivity analysis showed a range of savings between US$288 and US$661 in a 95% confidence interval. CONCLUSIONS For patients with DM2, treatment with Insulin Glargine is an efficacious and cost-saving option compared with ID, because Insulin Glargine is associated with a comparable efficacy and tolerability and lower annual total costs, allowing savings of up to US$474.7 per patient-year which represents 35.2% of the overall cost of insulin per patient-year.