This paper is an attempt to systematize the experimental results obtained in studying medium- energy ion scattering by solid surfaces. We confine ourselves to the analysis of only one definite interval of primary ion energies-from several keV to several hundreds of keV. This is due to several reasons. First, only this energy interval has been investigated in most detail. Second, only in this interval are the experimental data obtained by various authors in a good agreement. Therefore one can draw well-founded conclusions concerning the mechanism of medium-energy ion scattering by solids. Finally, the scientific interest of the authors is of certain importance when choosing the given energy interval.