Energy spectra have been measured of 1H and 4He projectiles backscattered from thin Au films of known thicknesses. An analytical expression for the spectra is derived in the limit of no multiple scattering. Protons of energies ~50 keV are shown to give resolutions of a few Å for depth measurements up to about 500 Å, thus providing a useful technique for studying surface regions. The technique is illustrated by measurements of a nickel film before and after oxidation. Stopping cross sections for 1H and 4He in Au are obtained for energies 20 < E < 100 keV.