For over forty years, coronary artery bypass grafting (CABG) has been recommended to patients with triple vessel disease (TVD) with the aim of providing a survival benefit compared to medical therapy. Generally, the survival benefit of CABG is determined by (a) the volume of myocardium at risk of infarction according to the extent of coronary artery disease (CAD), (b) the impairment of coronary flow reserve according to severity of coronary stenoses, severity of symptoms, or objective evidence of regional ischemia, and (c) the impairment of myocardial reserve according to left ventricular function and viability. The most frequently used index of survival benefit is the extent of CAD as described by the terms of the left main coronary stenosis and TVD. However, TVD has been inconsistently defined in randomised controlled trials. Furthermore, international guidelines do not provide a specific definition of TVD. This impacts a substantially sized and high-risk population. Here, we argue that the definition of TVD should include diseases in the major artery in each of the three coronary territories in order to estimate the survival benefit provided by CABG.