Although it was generally agreed that many patients with severe angina pectoris improved symptomatically after coronary artery surgery, there was less consensus concerning, for example, other effects of the procedure, such as its long-term benefit and the criteria for patient selection. In addition, there were fewer data and less agreement on the effects and proper role of this procedure in other clinical circumstances. Both the surgical procedure and the prior diagnostic procedures represented substantial costs in both monetary and manpower terms; moreover, they entailed morbidity and mortality risks.