OBJECTIVES We assessed the potential health and economic benefits of reducing common risk factors in older Americans. METHODS A dynamic simulation model tracked a national cohort of persons 51 and 52 years of age to project their health and medical spending in prevention scenarios for diabetes, hypertension, obesity, and smoking. RESULTS The gain in life span from successful treatment of a person aged 51 or 52 years for obesity would be 0.85 years; for hypertension, 2.05 years; and for diabetes, 3.17 years. A 51- or 52-year-old person who quit smoking would gain 3.44 years. Despite living longer, those successfully treated for obesity, hypertension, or diabetes would have lower lifetime medical spending, exclusive of prevention costs. Smoking cessation would lead to increased lifetime spending. We used traditional valuations for a life-year to calculate that successful treatments would be worth, per capita, $198,018 (diabetes), $137,964 (hypertension), $118,946 (smoking), and $51,750 (obesity). CONCLUSIONS Effective prevention could substantially improve the health of older Americans, and--despite increases in longevity--such benefits could be achieved with little or no additional lifetime medical spending.