To determine the prognosis of patients with coronary artery disease who have no or mild symptoms, such patients have been followed prospectively. Patients with single and double vessel disease have had an excellent prognosis. However, prognosis of patients with three vessel disease has been poor. Patients with three vessel disease who manifest poor exercise capacity have an annual mortality of 9%; those who manifest a good exercise capacity have an annual of 4%. This contrasts to an annual mortality of only 1.5% in those patients with single or double vessel disease.