The scientific foundations for risk factor modification in the elderly are three-fold: (1) data from long-term prospective population studies demonstrating significant independent relationships between established major risk factors—particularly blood pressure (systolic and diastolic), serum cholesterol, cigarette use, clinical diabetes—and risk of cardiovascular (CV) morbidity and mortality; (2) data from population studies on time trends of mass changes in major risk factors and parallel changes in CV mortality rates, including large sustained declines; (3) data from randomized controlled trials (RCTs). RCTs, the focus of this presentation, have been both unifactorial and multifactorial. The former include several trials of antihypertensive drug treatment, and of diet or drugs to lower serum cholesterol. When each of these two sets of unifactorial trials is considered in its totality, the positive nature of the findings is apparent. Among the antihypertensive drug trials, two—the Hypertension Detection and Follow-up Program in the U.S.A. and the study by the European Working Party on High Blood Pressure in the Elderly—involved older men and women, both with significantly favourable outcomes for their intensive treatment groups. Among the several trials on serum cholesterol reduction, the Los Angeles Veterans Administration domiciliary study involved elderly men, and showed significant reductions in incidence and mortality from atherosclerotic events in its fat-modified diet group. Multifactorial trials have involved middle-aged men. Their findings are generally positive, particularly in regard to efficacy of life-style interventions to modify diet and smoking habits. Degree of efficacy is apparently related to degree of net change in risk factors in the intervention group compared to the control group. All these findings lend strong support to the judgment that risk factor modification, in the elderly as well as at younger ages, is useful for the prevention of the major adult CV diseases and for increasing longevity with health.