In the present report, we review the phenotypes of coronary artery disease (CAD) patients unsuitable for revascularization procedures. We then analyze these phenotypes and propose a simple angiographic-based classification for patients with CAD unsuitable for revascularization. Under this classification, the following four distinct angiographic phenotypes are proposed: (1) suspected cardiac syndrome X; (2) limited territory at risk; (3) diffuse thread-like coronary atherosclerosis; and (4) end-stage CAD. It is hoped that such a classification system, as well as the general principles described in this report, will help to standardize the collection of epidemiological data on patients with refractory angina (RFA) and advanced CAD. It is also hoped that this system will be useful to extend the principles of clinical equipoise to the development of clinical trials of innovative therapies or devices for the treatment of RFA. Finally, we anticipate that the elaboration of this system, the first of its type in the literature, will stimulate discussion of what we feel to be a subject that has received insufficient attention in the literature, and ultimately to improved management of a challenging patient population.