The identification of the proximal causes of coronary heart disease (CHD) during the second half of the 20th century contributed to the prevention of premature CHD and the extension of life expectancy in middle-aged and older people in many wealthy countries. These major CHD risk factors-high blood cholesterol, high blood pressure, cigarette smoking and physical inactivity-satisfy public health criteria of causality. Strong epidemiological evidence suggests that they explain at least 75% of new cases of CHD. However, the search for 'new' or 'emerging' CHD risk factors continues, partly justified by a myth that minimizes the contribution of the major risk factors. The public health criteria of causality were applied to the following proposed new risk factors: thrombotic factors and serum homocysteine levels; infectious agents; early life exposures including prenatal factors; genetic influences; oestrogen deficiency; and the role of the psychosocial environment. None of these factors are as important as the established risk factors for epidemic CHD and their potential contribution for improving population health is limited or unclear. Research into unexplained variations in the occurrence of CHD and into life course influences and socioeconomic inequalities may provide extra leads to effective public health action. Especially important is research on the upstream social and economic determinants of CHD and its major risk factors, on the spread of the CHD epidemic to poorer populations, and into prevention policy and programme effectiveness. Available evidence supports the feasibility and effectiveness of population-wide prevention directed towards increasing the proportion of people at low risk of CHD. The vast majority of the public health effort should be directed to this approach rather than to the high risk individual approach. There is still a major gap between knowledge and action in preventing the CHD epidemics.