Most individuals with arterial hypertension or congestive heart failure are insulin-resistant and at a higher risk of developing type 2 diabetes (T2DM). The inhibition of the renin-angiotensin system (RAS), using an angiotensin converting enzyme inhibitor (ACEI) or a selective angiotensin receptor AT1 blocker (ARB), may exert favourable metabolic effects capable of preventing T2DM in high risk individuals. We performed a meta-analysis of randomised clinical trials (RCTs) assessing the effects of RAS inhibition on the incidence of new cases of T2DM in patients with arterial hypertension or congestive heart failure. Ten RCTs with cardiovascular prognosis as primary endpoints analysed the incidence of T2DM as secondary endpoints or as post-hoc analysis after a mean follow-up of 1 to 6 years: five with an ACEI and five with an ARB, compared with a placebo (n=4) or a reference drug (beta-blocker or diuretic: n=5; amlodipine: n=2). Eight RCTs concerned hypertensive patients: STOP Hypertension-2 (lisinopril or enalapril vs beta-blocker or diuretic), CAPPP (captopril vs thiazide or beta-blocker), HOPE (ramipril vs placebo), ALLHAT (lisinopril vs chlorthalidone and lisinopril vs amlodipine), LIFE (losartan vs atenolol), SCOPE (candesartan vs placebo), ALPINE (candesartan vs placebo) and VALUE (valsartan vs amlodipine). Two RCTs concerned patients with congestive heart failure: SOLVD (enalapril vs placebo) and CHARM-overall programme (candesartan vs placebo). Overall, 2 675 new cases of T2DM (7.40%) were observed in the group of 36 167 patients receiving a treatment with ACEI or ARA as compared with 3 842 events (9.63%) in the group of 39 902 control patients. A mean weighed relative risk reduction of new T2DM of 22% (95% CI: 18, 26; p<0.00001) was observed after RAS inhibition. The beneficial effect was similar with ACEIs and with ARBs as well as in patients with hypertension and in those with heart failure, and was also present whatever the comparator (placebo or beta-blockers/diuretics or amlodipine). The number needed-to-treat to avoid one new case of T2DM averaged 45 patients over 4-5 years. In conclusion, RAS inhibition consistently and significantly reduces the incidence of T2DM in individuals with arterial hypertension or with congestive heart failure. Considering the pandemic of T2DM, such pharmacological approach deserves further attention among the strategies aiming at preventing T2DM.