A basic principle of prevention is that the intensity of risk-reduction should be adjusted to a person's absolute risk. Atherosclerosis (ATS) is a progressive disease associated with cardiovascular complications such as coronary heart disease (CHD), stroke and peripheral arterial disease. ATS may, however, remain asymptomatic for many years, with sudden death being its first clinical manifestation. Primary prevention of cardiovascular diseases (CVD) offers the greatest opportunity for reducing the burden of CVD. The selection of patients for clinical intervention for prevention of CVD is done through identification of high-risk conditions and risk factors (RF) for CVD. Three categories of RF that contribute to CVD risk include underlying RF, major RF and emerging RF. Assessment of absolute risk gives priority to the major RF alone. The usual method for estimating absolute risk is to determine ten-year risk for hard CHD events (myocardial infarction + coronary death) or cardiovascular mortality. Absolute risk for total CVD events (acute coronary syndromes, coronary death, coronary procedures, and stroke) typically is about twice that estimated for hard CHD events. Categories of ten-year risk warranting clinical intervention vary according to national health policy. Aten-year risk for CHD of >20% is commonly classified as a high risk status. ATP-III and IAS guidelines further identify a ten-year risk of 10-20% as intermediate risk status and a ten-year risk for CHD <10% as low risk status. ESC guidelines stratify patients in high risk category for fatal CVD events ≥5% over the next ten years and in low risk category for fatal CVD events <5%. Several risk-assessment algorithms have been developed for estimating the absolute risk for CVD. In Switzerland, IAS-modified for Switzerland or ESC guidelines are recommended for daily use in clinical practice.