The perfectly matched layer, PML, is a new technique developed for the simulation of free space with the finite-difference time-domain (FDTD) method, This paper deals with the application of this technique to the solution of wave-structure interaction problems, It is shown that the absorbing layer can be set very close to the structure, provided some specifications are satisfied, with the consequence that the computational requirements of the PML technique are far shorter than those of the other methods of free-space simulation.