The dynamics of continuous media subjected to initial stress is of great interest in several fields of applied science and technology: geophysics, oceanography, underwater acoustics, and structural design. Pioneering analytical work in this field was done by M. A. Biot. Few contributions have been made, however, to the experimental treatment of the problem of determining dynamic stress distributions within statically prestressed continuous media. This study deals with an experimental analysis of the propagation of flexural waves in prismatic elastic bars with and without prestressing. The effects of prestressing by axial tension, axial compression, and pure bending are illustrated. Comparisons are made with an approximate theory. The results are extended to bars of other materials by scaling laws.