Abstract Direct measurements of depth resolution in Rutherford backscattering analysis have been made in C, Al, and Cu targets as a function of analysis depth for 2 MeV 4He + backscattering at a low-angle scattering geometry, employing a solid-state detector. Similar measurements have been made using 500 keV 4He + and a magnetic spectrometer as a detector. The optimum depth resolution as a function of obtained with both systems is comparable; typically, 25 Å for surface analysis and falling to 120 Å at an analysis depth of 1000 Å. Estimates of depth resolution have been made from simple theoretical calculations, and these are found to be in good agreement with the measurements, suggesting that simple estimates can be used to reliably predict the analysis conditions which provide maximum depth resolution. Additionally combinations of low-angle scattering geometry and a high energy-resolution magnetic spectrometer are investigated and shown to have advantages for surface analysis, where better than 10 Å resolutions seem possible.