Photoelectrochemlcal and semiconductor properties of cadmmm sulphde fdms grown on cadnnum m alkaline sodium sulphlde solutions were characterized by measurements of capaatances, photopotentlals and photocurrents as functions of film thickness, wavelength and electrode potential These propeties were smular to those of CdS single crystals apart from effects of the disordered lattice Donor den&es were of the order 10's cn1-'-10'~ cm-)decreasmg with film thickness The photocurrents grew linearly Hnth (hv -e,,.!Q2 for wavelengths < 5 1 1( f 5) nm correspondmg to a band gap energy of about eOEs = 2 42 eV m agreement with measurements of photopotentlals At > 5 11 nm an Urbach tall of the photocurrents was observed The dependence of the photocurrents on the electrode potential was character&c of the Poole-Frenkel effect Illummatlon increased the current efficlencles for the dlssolutlon of cadmium ions and to a mmor degree of the oxidation of sulphlde to polysulphlde Accordmgly, the current efficiency for film growth was decreased Photoeffects were not observed m the first 1 3 nm of the film adjacent to the metal due to a negative space charge layer