The actuarial survival curves of "medically treated" patients whose arteriographic studies demonstrated coronary arterial lesions of various degrees-- now used widt applicable to the asymptomatic patient. No information is available regarding the course or prognosis of the asymptomatic patient with demonstrated lesions in the coronary arteries. For the reasons explained one can propose a hypothesis that the overall prognosis of this type of patient is better than average, probably better than that shown in the best data collected on symptomatic patients. The prophylactic value of aortocoronary bypass operations in preventing myocardial infarction and death has not been established. One can therefore question the justification for the wide case-finding effort of subjecting asymptomatic persons to coronary arteriography, even in light of the low risk of this procedure, unless unusual findings suggest an especially poor prognosis (one example might be past myocardial infarction in a very young patient). Although there are exceptional instances when prophylactic surgery is indicated for asymptomatic patients, further investigation of this subject is needed before the procedure becomes generally accepted.