The development of new-onset diabetes is frequent during the follow-up of treated hypertensive patients. The prevalence of such an event seems to differ depending on the type of antihypertensive therapy used to control blood pressure. Diuretics and b-blockers and their association are particularly harmful in this regard. On the contrary, calcium channel blockers, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, alone or in association with diuretics, are associated with a lower prevalence of this metabolic complication. These statements are confirmed by data from the Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) study. Long-term studies are required to determine the relevance of development of new-onset diabetes in treated hypertensive patients.