Although many cases of prosthetic valve malfunction have appeared in the literature, statistically significant reports of the noninvasive diagnosis of valve malfunction are few. Metal-and-plastic mitral valves may be evaluated by a combined echocardiographic and phonocardiographic approach. Analysis of the A2-MVO interval seems to provide the most amount of information; supportive data useful in identifying the cause of valve malfunction come from phonocardiographic murmur and echocardiographic wall motion analysis. Additional cases of valve dysfunction will be detected if spectral analysis and cinefluoroscopy are also used. Suspected cases of mitral prosthetic malfunction must always be differentiated from left ventricular dysfunction; this may require invasive study. There is no evidence that two-dimensional echocardiography has any use in the analysis of metal-and-plastic mitral valves. There is no evidence that any noninvasive technique, particularly echocardiography, can consistently detect metal-and-plastic aortic prosthesis malfunction, especially of the tilting-disc type of valve. Noninvasive evaluation of tissue heterograft valves in the mitral and aortic positions require combined M-mode and two-dimensional echocardiographic study. Morphologic and functional alteration in these valves can be detected. Most importantly, accurate analysis of any particular valve requires an understanding of the individual clinical setting.