By 1979, mortality rates for coronary heart disease had declined for 14 consecutive years in the United States. Preliminary data indicate a continued decline. This review of reports published in the last five years documents the consistency of most data with the following hypotheses: (1) Reductions in population levels of hypertension and cigarette smoking have contributed to the decline in mortality from coronary heart disease. (2) Improved medical care for acute myocardial infarction has also contributed to the decline. Data are lacking to specify the contributions of changes in other risk factors, emergency medical services, medical care of chronic coronary heart disease, or other changes in the physical and social environment. Long-term, simultaneous surveillance of mortality, morbidity, medical care, and risk factors should be supported in five to 10 centers around the United States.