Single coronary artery is a fairly rare entity which may nevertheless be found in 0.4 per cent of coronary arteriograms. The authors report 3 cases seen in 2 departments of cardiology. In each patient, despite the existence of definite cardiovascular risk factors, this distribution was a factor worsening coronary ischemia, leading to complete thrombosis in one case. Although most often a chance discovery, a review of the literature justifies the attribution to this anomaly of the onset of angina, infarction or even sudden death.