A large scale, prospective, randomized study of surgical v. medical management of disabling angina pectoris is being conducted as a cooperative study among thirteen Veterans Administration hospitals in the U.S.A. A total of 1015 patients have been entered into the study and follow-up data are currently being evaluated. Patient entry into the study was concluded in December 1974. Patient compliance has been acceptable with only 7% of patients not adhering to their randomization category. Thirty-day operative mortality (1972-1974) in 309 patients was 5-3%. The patient population exhibited a severe degree of coronary disease. There was ECG evidence of prior myocardial infarction in 40%. There were significant obstructive lesions in three major coronary arteries in 51% and significant lesions of the left main coronary artery in 11%. Medical and surgical treatment groups demonstrated no significant differences in objective descriptive characteristics. Mortality in the medical group at 1 year was 8%. Mortality was influenced by several factors including the number of vessels involved, left ventricular function and the presence of left main coronary artery disease. The lowest mortality occurred in patients with single vessel disease and normal LV function who had a 1-year mortality of 3%. Patients with 3-vessel disease and abnormal LV function exhibited a 14% 1-year mortality. Patients with disease of the left main coronary artery and poor LV function had a 1-year mortality of 37%. Analyses of the results of treatment modalities in sub-groups is currently being performed and will be reported in future publications.