A novel, comprehensive health risk index for adults has been validated and is now ready for use to improve the health of individuals and populations. This health risk index provides an estimate of the avoidable risk of death for adults 30 years or older. It includes 12 evidence-based clinical and behavioral risk factors and was validated on discrimination and calibration using the NHANES (National Health and Nutrition Examination Survey) and Framingham Heart Study cohorts. The results from both cohorts were consistent and similar. Discrimination was good, and calibration was acceptable but tended to overpredict mortality risk for females in the higher-risk deciles.