  We study the theory of scattering for the Wave-Schr"odinger system with
Yukawa type coupling in space dimension 3. We prove in particular the existence
of modified wave operators for that system with no size restriction on the wave
data in the framework of a direct method which requires smallnes of the
Schr"odinger data, and we determine the asymptotic behaviour in time of
solutions in the range of the wave operators.
