The phonocardiography method is appraised and the correlative dependence of the data yielded by it is compared with the hemodynamic values in the diagnosis of paravalvular fistulas following mitral valve prosthetics in 11 patients. It was revealed that the duration of the interval from the sound of aortic closure to the sound of mitral opening is in close reverse relation (r = -0.61) with the level of the mean pulmonary-capillary pressure: the shorter the interval, the more severe is the disorder of hemodynamics in patients with paravalvular mitral insufficiency and the higher is the mean pulmonary-capillary pressure. Paravalvular fistulas in the 11 patients examined were manifested by the development of a systolic murmur.