[en] CdS crystals exhibit two kinds of photoreflectance spectra which are classified as type A and type B. Surface-sensitive experiments show these spectra to be induced or influenced by surface electric fields. Type A spectra are favoured if an enhancement layer is present and type B spectra if there is a depletion layer. These spectra can be transformed from one type into the other by additional electric fields or temperature treatment of the crystals. Although a similar behaviour of CdS is known from photoconductivity experiments, a direct relation between photoconductivity and photoreflectance is questionable. (author)