Research advances are generating a growing body of clinical trial and other data on the effects of tests and treatments on outcomes, but there is no information resource within the health care system that systematically puts that information in perspective. Policy makers, clinicians, and individuals lack a ready means to compare the relative effectiveness of various interventions in prolonging survival or preventing the occurrence or complications of a disease: information that is critical in setting priorities. A crude analysis of preventable deaths suggests that evidence-based primary prevention (getting the population to stop smoking, exercise, lower cholesterol levels, and control blood pressure) would prevent considerably more deaths per year than would various evidence-based treatments for cardiovascular disease. Examining evidence from this perspective calls attention to mismatched priorities-most health care expenditures in the United States go toward treatment of diseases and their late-stage complications and relatively few resources are devoted to primary prevention and health promotion. Similar analyses at the individual level can help patients put personal options in perspective. This article proposes a bibliographic evidence-collection center and simulation modeling program to estimate potential benefits and harms of competing interventions for populations and individuals. Such evidence-based projections would enable policy makers, clinicians, and patients to judge whether they give due priority to the interventions most likely to improve health. With the steady growth in research data, the need for a system that enables society and individuals to put evidence in perspective will become progressively more urgent.