Epidemiology involves the study of disease frequency and its determinants within the population. Cardiovascular epidemiology began in the 1930s as a result of changes observed in the causes of death. In the 1950s, several epidemiological studies were set in motion with the aim of clarifying the cause of cardiovascular disease. Four years after the Framingham Heart Study started, researchers had identified high cholesterol and high blood pressure levels as important factors in the development of cardiovascular disease. In subsequent years, the Framingham study and other epidemiological studies have helped to identify other risk factors, which are now considered classical risk factors. By coining the expression "risk factor", the Framingham Heart Study helped to bring about a change in the way medicine is practiced. Today, a risk factor is defined as a measurable characteristic that is causally associated with increased disease frequency and that is a significant independent predictor of an increased risk of presenting with the disease. This wide-ranging overview describes some of the most important insights into the causes of cardiovascular disease to have come from the Framingham Heart Study. The emphasis is on the identification of risk factors, and the assessment of their predictive ability and their implications for disease prevention.