The prevalence of diabetes mellitus is increasing worldwide. Among other complications, diabetes is associated with the risk of coronary heart disease (CHD) that is thought to be equal to the risk of CHD in subjects without diabetes with previous myocardial infarction. Studies have shown that CHD risk factors start to increase long before the onset of clinical diabetes. Furthermore, the risk factors that are present in prediabetic individuals are also components of the highly prevalent metabolic syndrome. This suggests that treatment of CHD risk factors may effectively reduce the incidence of type 2 diabetes. Lifestyle interventions have proved effective in preventing the onset of type 2 diabetes in subjects with impaired glucose tolerance. A number of post hoc studies have reported consistent reductions in the incidence of type 2 diabetes in hypertensive patients treated with either angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs). As a result of these positive data, ongoing prospective studies are investigating whether antihypertensive agents prevent or delay the onset of diabetes in patients at risk. Telmisartan, a selective oral ARB that is indicated for first-line therapy of essential hypertension, may provide improved tolerability compared with ACE inhibitors. Therefore, the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET) program is investigating the effectiveness of telmisartan in the prevention or delay of type 2 diabetes. The program comprises ONTARGET and the Telmisartan Randomized Assessment Study in ACE-Intolerant Subjects with Cardiovascular Disease (TRANSCEND).