The measurement of target thicknesses and impurity contents using backscattering, as well as the principle of this technique are briefly described. The targets are irradiated in a beam of 2 MeV 4He + ions. The backscattered ions are detected using a Si(Au) solid-state detector. Gold and calcium fluoride on thin carbon backing and selfsupporting silicon foils were determined from peak width measurements. Oxygen and tungsten impurities in a silicon target being prepared by vacuum evaporation from a tungsten boat were determined using the same method. The thickness of a thin aluminium deposit on thick tantalum backing was obtained from the energy shift of the tantalum peak between two spectra recorded with respectively the aluminium and the tantalum facing the ion beam. Copper contamination on the surface on an iron layer electroplated on copper foil was determined by comparison of the copper peak area with the iron peak height in the backscattering spectrum.