Thirty patients with 33 mitral or aortic prostheses or both were examined using the pulsed Doppler technique combined with cross sectional echocardiography to study the applicability of the Doppler technique in the diagnosis and evaluation of the severity of prosthetic dysfunction and to assess the ability of the mapping procedure to estimate the site and the size of the prosthetic defect. The dysfunction was valvar regurgitation in 29 instances and stenoses in eight, all of which were confirmed by invasive procedures. The severity of the dysfunction was graded on a three point scale. A control group of 73 subjects with 88 normal prostheses also underwent pulsed Doppler and cross sectional echocardiography. The pulsed Doppler study followed the usual procedure for a valvar disease including two and three dimensional mapping for regurgitation. Eight patients also underwent a continuous wave Doppler examination. The diagnostic reliability of the pulsed Doppler technique was greater than or equal to 90%. The severity of the dysfunction was accurately assessed in 86% of cases. In the case of aortic regurgitation, mapping of the jets was performed as easily for prostheses as for native regurgitant valves. In the case of mitral regurgitation, the mapping patterns depended on the cause of the dysfunction. With valvar tears, a jet was detected at the centre of the annulus, and with paravalvar leaks eccentric atrial jets were seen opposite the site of the leak. The pulsed Doppler and the surgical findings correlated well for both the site of the dysfunction (16/20 (80%) patients) and the size of the leak (13/16 (81%) patients). Thus, despite some limitations, pulsed Doppler and particularly the mapping procedure provide sufficient information to give an accurate non-invasive assessment of prosthetic valve dysfunction.