Abstract : Sitagliptin (Januvia®), the first selective inhibitor of dipeptidylpeptidase-4 with a so-called incretin effect, has been evaluated in SUGAR, a large Belgian prospective observational study carried out in general practice. Sitagliptin, at a dose of 100 mg once daily, was added to previous treatment of not well controlled type 2 diabetic patients (> 95 % on metfor-min monotherapy). Among 605 patients analysed in intention to treat, the worse the glycaemic control at entry, the greatest the reduction in glycated haemoglobin (HbA1c) and fasting plasma glucose levels after the addition of sitagliptin (p < 0.001). No specific factor was associated with the quality of initial glucose control among age, body mass index, the duration of diabetes or the modalities of its pharmacological treatment. Similarly, among these factors, none was significantly associated with the reduction in HbA1c or fasting plasma glucose levels observed with the addition of sitagliptin. Thus, sitagliptin was as active in older as in younger subjects, in obese as in nonobese people and in patients with diabetes of long versus short duration. In particular, SUGAR recruited data on 191 patients above 70 years in whom sitagliptin was as effective and safe as in younger patients with type 2 diabetes.