SUMMARY A 72-year-old man with calcific aortic stenosis and complete heart block was noted to have an intermittent diastolic murmur. Using combined echocardiography and phonocardiography, it was demonstrated that the murmur occurred while the mitral valve was closing. This suggested that antegrade flow across a closing mitral orifice is of etiologic importance in the production of the murmur. Atrial sounds were also recorded and probably have a similar etiology. It is postulated that reduced ventricular compliance resulting in a more rapid rate of mitral valve closure was of etiologic importance in the genesis of the murmur.