At present there are many different prosthetic models available for heart valve replacement. Postimplant dysfunction resulting from material failure has been reported in several prostheses. The prime cause of these defects is hidden abnormalities in the valve construction or materials. In order to detect these defects before implantation, preoperative non-destructive testing of individual valves is proposed. For this purpose, holographic interferometry has been applied which is a non-contact, non-destructive, highly sensitive, three-dimensional measurement technique. Samples of different types of prosthetic heart valve, both mechanical and biological, were mounted in a specially developed test chamber with optical access from four sides. The valves were loaded with a static liquid pressure of 2.5-15 kPa. Deformations of the valves as a result of small pressure differences (0.5-15% of the static pressure) applied between two exposures were recorded by double-exposure holography. A fringe pattern superimposed on the image of the valve reconstructed from the hologram clearly indicates the presence of defects in the valve material.