For more than 25 years, there has been an expansion in the clinical and experimental evidence linking hyperinsulinemia with cardiovascular disease and atherosclerosis. Assessment of the evidence under the headings of the strength of the association, dose response, temporality, consistency, specificity, and plausibility supports the concept that hyperinsulinemia has a causal role in atherogenesis. Evidence that reducing insulin levels prevents atherosclerosis is lacking. The evidence available is strong enough to support preventive measures to lower insulin levels such as regular physical exercise and avoidance of obesity.