Multiple factors contributing to coronary heart disease (CHD) and underlying atherosclerosis have been identified. Biologic factors include aging, gender, and family history. Potentially modifiable risk factors are: cigarette smoking; high blood pressure; elevated levels of plasma total and low density lipoprotein and low levels of high density lipoprotein cholesterol; diabetes mellitus; obesity; dietary habits; physical inactivity and poor physical fitness; and perhaps response to psycho-social stress. CHD risk increases with the number of risk factors and their levels. Resting and exercise ECG abnormalities further increase risk. Because of differences in levels of these risk factors, a great deal of variability exists in probability of CHD at any age. Using age alone to predict risk of heart attack results in high rates of false positives. Favorable alterations in modifiable risk factors by the American public appears to be primarily responsible for the progressive decline in CHD mortality rates in this country since 1968. This decline has occurred at all ages during a period of dramatic increase in prevalence of people over 65 yr of age in the United States. This confirms that modifiable risk factors are much more important than age in the etiology of CHD, and clearly demonstrates that CHD is not an inevitable part of the aging process.