A new method for measuring specific energy losses in pure polycrystalline materials is presented and applied to the stopping of protons in gold in the range 350–650 keV. Two backscattering spectra were obtained from a thick gold target through which the protons passed with the target first tilted towards and then away from the particle detector, the angle of incidence of the proton beam being the same in both cases. The widths of the spectra were evaluated by fitting a theoretical spectrum to the measured curve taking account of the resolution function of the surface barrier detector and of the depth-dependent energy loss straggling. From the difference of the energy widths of the two spectra the stopping cross section can easily be evaluated. The results are in good agreement with all recently published data.