The authors have reviewed the literature in search of the coexistence of single coronary artery with significant coronary artery disease. Two cases of single right coronary artery are described. In both, the anomalies were unsuspected and diagnosed roentgenographically in life. Both patients had angina pectoris, positive graded-exercise stress tests, and hemodynamically significant obstruction or occlusion to the coronary arteries. In neither case was the stenosis proximal or amenable to bypass surgery.