A classical mechanical computer simulation of the emission of low energy protons from a single crystal surface of potassium chloride is described. Comparison of the results is made with experimental observations obtained in reflection and transmission at 30 keV. It is concluded that classical mechanics adequately explains the observed features down to energies as low as 5 keV, in keeping with a “correspondence principle” previously outlined. Brief discussion is made of the usefulness of the back scattering technique.