This article summarizes an important study published in 2006 in the field of the prevention of diabetes mellitus. It is the DREAM study which evaluate the therapeutic effects of rosiglitazone and ramipril versus placebo in the prevention of type 2 diabetes in high risk patients: glucose intolerance or impaired fasting glucose. In this clinical study, more than 5000 patients were followed during 3 years. The risk of diabetes was reduced with rosiglitazone of 62% (NNT 9). In the field of negative effects the risk of cardiac insufficiency was multiplied by 7 (NNH 250) but stayed a rare event (to 0,5% of the treated subjects). The ramipril had no preventive effect for the prevention of type 2 diabetes but induced a higher frequency of return towards the normoglycaemia. This treatment can be recommended for these high risk subjects.