A consecutive series of 14 708 coronary arteriograms, performed between 1 April 1975 and 1 August 1983 was examined for the presence of coronary artery fistulas. The incidence was 0.13. There was 1 traumatic and 19 congenital cases. All fistulas were small and of little haemodynamic significance. No symptoms or complications could be ascribed to these fistulas. In the large majority no continuous or other murmurs suggested their presence. The large majority arose from the proximal anterior descending artery and emptied in the pulmonary artery. Surgical treatment for these fistulas is not indicated.