A method for the rapid estimation and display of coronary risk is used in counseling and for following progress in the practice of preventive cardiology. The estimator is a slide rule which computes risk of a future coronary event based on current age, smoking habit, serum cholesterol, and blood pressure levels. The device also displays estimated change in risk based on change in risk factors. The estimates are explained to clients as gross approximations. The slide rule is helpful in personalizing the need and the potential of preventive efforts.