A case of anomalous origin of the left coronary artery from the pulmonary trunk is reported. The patient, a 64-year-old woman, presented with a history of angina and cardiac failure. She was known to have had a mitral systolic murmur since school age. Echocardiography showed clinically significant mitral regurgitation and highly unusual extensive calcification of the mitral valve chordae, papillary muscle, and posterior left ventricular wall--a pattern suggesting the possibility of abnormal coronary circulation. Subsequent cardiac catheterisation confirmed considerable mitral regurgitation with a dilated left ventricle, and arteriography confirmed anomalous origin of the left coronary artery from the main pulmonary trunk. The patient was surgically treated with ligation of the origin of the anomalous left coronary and mitral valve replacement. She was alive and well 2 years after operation.