Between 1972 and 1975, 1832 middle-aged men (40 to 59 years), apparently healthy with no subjective complaints related to heart disease, underwent extensive noninvasive cardiovascular examinations. Additionally, 50 asymptomatic men with an ischemic reaction in the ECG who were subsequently found to have angiographically-documented coronary artery disease, together with the remainder of the cohort, had regular follow-up examinations in yearly intervals. The total observation period ranged up to 14.5 years. In the group with silent ischemia, at 7.5 years, only 17 of the 50 patients had no evidence of progression and the incidence of cardiac events increased continuously thereafter such that at 13.5 years, only six of the 50 had remained stable. At this time, twelve had died (three within the first 7.5 years) and 13 had undergone bypass surgery. The rate of cardiac events in the group with silent ischemia was four to five times higher than that in those with no manifest disease. The study shows that documentation of myocardial ischemia in asymptomatic patients is indicative of the presence of coronary artery disease and is associated commonly with progression of the disease in spite of the absence of angina pectoris.