The last 20 years have provided an extraordinary amount of data contributing to an improved understanding of the prognosis of chronic ischemic heart disease. However, much remains incompletely understood. The lack of more precise knowledge about prognosis encourages fuzzy clinical thinking and seems to justify the overutilization of a variety of diagnostic and therapeutic modalities. It seems probable that the information available on many individual patients is not fully utilized in assessing prognosis more accurately. An approach is outlined which attempts to utilize clinical and laboratory data in prognosis with particular emphasis on objective information concerning left ventricular function and evidence of myocardial ischemia. The importance of transition phases in the natural history of the patient with ischemic heart disease is emphasized. Table V attempts to summarize areas of clinical research which are important if we are to gain a better understanding of the prognosis of this unusually complex clinical entity, chronic ischemic heart disease.