The authors report two cases of single coronary artery arising from the right coronary sinus. Both patients had angina with reversible myocardial ischaemia on exercise Thallium scintigraphy. Coronary angiography showed single coronary artery arising from the right coronary sinus in both cases with severe stenosis of the right coronary artery in the first and occlusion of the right coronary artery in the second patient. Both underwent surgical revascularisation with a good result. Single coronary artery is a rare congenital abnormality (approximately 0.36 per 1,000) diagnosed at autopsy until 1963, and thereafter at coronary angiography. A review of the literature shows that an equal number of single coronary arteries arise from the right as from the left coronary sinus: there does not seem to be an increased risk of complication when a branch runs between the aorta and pulmonary artery. On the other hand, single coronary arteries arising from the right coronary sinus seem to be more commonly associated with atherosclerosis than a network with two coronary arteries, but when the lesions are proximal, the risk is high. Revascularisation is indicated only when myocardial ischaemia has been documented.