We investigated whether protection from coronary heart disease (CHD) and stroke conferred by angiotensin-converting enzyme inhibitors (ACEIs) and calcium channel blockers (CCBs) in hypertensive or high-risk patients may be explained by the specific drug regimen. We extracted summary statistics regarding CHD and stroke from 28 outcome trials that compared either ACEIs or CCBs with diuretics, beta-blockers, or placebo for a total of 179,122 patients, 9509 incident cases of CHD, and 5971 cases of stroke. CHD included myocardial infarction and coronary death. In placebo-controlled trials, ACEIs decreased the risk of CHD (P<0.001), and CCBs reduced stroke incidence (P<0.001). There were no significant differences in CHD risk between regimens based on diuretics/beta-blockers and regimens based on ACEIs (P=0.46) or CCBs (P=0.52). The risk of stroke was reduced by CCBs (P=0.041) but not by ACEIs (P=0.15) compared with diuretics/beta-blockers. Because heterogeneity between trials was significant, we investigated potential sources of heterogeneity by metaregression. Examined covariates were the reduction in systolic blood pressure (BP), drug treatment (ACEIs versus CCBs), their interaction term, sex, age at randomization, year of publication, and duration of treatment. Prevention of CHD was explained by systolic BP reduction (P<0.001) and use of ACEIs (P=0.028), whereas prevention of stroke was explained by systolic BP reduction (P=0.001) and use of CCBs (P=0.042). These findings confirm that BP lowering is fundamental for prevention of CHD and stroke. However, over and beyond BP reduction, ACEIs appear superior to CCBs for prevention of CHD, whereas CCBs appear superior to ACEIs for prevention of stroke.