A new experimental technique has been used to measure the stopping power of CdS for He ions. This technique consists of measuring the energy spectrum of either He ions backscattered from implanted Bi or of &agr; particles emitted by an implanted radioactive isotope, such as Po210. A thin layer is then etched off the surface of the sample and the energy spectrum is measured again. The stopping power is calculated from these two spectra and the known thickness of the removed layer. These measurements and calculations have been made for energies ranging from 0.963 to 5.3 MeV with accuracies between 12% and 16%.