Indium nitride (InN) and tin nitride (SnNx) films were produced with reactive d.c. magnetron sputtering technique. The thin film semiconductors were optically and photoelectrochemically characterised and the energetic positions of the two semiconductors' band edges were determined with respect to the normal hydrogen electrode. The sputtered InN thin film showed an indirect bandgap of 1.4 eV and a direct bandgap of 1.8 eV. The optical spectra of SnNx indicated a bandgap energy of approximately 1.4 eV. All nitride films showed n-type photoresponse in KI (aq) electrolyte at an irradiation intensity of 1000 W/m(2). The photoelectrochemical characterisation indicated that InN and SnNx with a bias of about 400 mV or less can be used for photo-oxidation of water. (C) 2002 Elsevier Science B.V. All rights reserved.