Coronary arteriography and coronary artery bypass surgery have provided a tremendous stimulus to learn more about the natural history of ischemic heart disease. It has become apparent that the most important approach to understanding prognosis involves placing patients into subsets. Clinical presentation is an entry into subsets but is an inadequate way to assess the problem. Anatomical information in the form of coronary arteriographic abnormalities and left ventricular functional abnormalities are powerful prognostic determinants. It remains important to consider matters such as increased blood pressure, cardiomegaly, and perhaps other factors such as cigarette smoking as additive to any anatomical information which can be obtained for any given subset. Premature ventricular contractions, particularly of the complicated type, may be a very powerful and important additive prognostic consideration in all patients with ischemic heart disease but especially those prone to sudden cardiac death. Coronary bypass, surgery now widely practiced in Western Europe and the United States, is an established, integral part of therapy for certain subsets of patients. It clearly cannot resolve the total issue of therapy and must be utilized selectively and critically along with other intensive medical measures to hope to control risk factors and progression of the coronary arteriosclerotic process.