The echocardiography of 25 patients with Björk-Shiley disc prosthesis (16 aortic, 7 mitralic, 1 both mitralic and aortic and 1 both mitralic and tricuspidal) was studied. Mitralic prosthesis were placed with the shortest disc segment looking forward; aortic prosthesis faced the shortest disk segment looking towards the coronaric sinus. The echo's morphology is related to the multiple relationships among position and direction of the prosthesis and the probe. In the aortic echocardiogram, it is possible to recognize echoes from the ring dissociated by anterior and posterior aortic walls. Between them echoes corresponding to the open disc appear, making a quadrangular figure. The values of the internal diameter of the ring obtained were very similar to the real value (difference 0-1 mm). Mitralic echocardiogram is characterized by the valvular disc movement tracing the typical quadrangular pattern, which is due to its opening and closure. Echoes of the supporting apparatus can be recorded directing the probe toward the heart base. In aortic and mitralic prosthesis, disc movements can be estimated. Opening and closure speed rate and their correlation vary on a large scale, both within different patients and in the same patient. Maximum disc excursion appears to be a more homogeneous and constant data in long-term controls and can be used to estimate valvular functionality: in aortic prosthesis valve the obtained value (mean = 17.46 +/- 0.53 "ES") is similar to the real diameter of the disc, in mitral prosthesis valve the value obtained (mean = 17.50 +/- 0.74 "ES") is shorter than the real value.