High-performance photocatalytic and photoresponsive properties have been made from composite ZnSnO3 nanowires. The composite nanowires consist of several phases, such as a major phase of ZnSnO3 and second phases of ZnO, SnO2, and metallic Zn nanowires. These nanowires formed many nanowire-to-nanowire junctions at the networking points of the ZnO/ZnSnO3/SnO2 interfaces; thus, a heterojunction cascade is obtained in the presence of these semiconductors. A charge transfer takes place at the composite nanowires under UV-light (lambda similar to 365 nm, I = 2.33 mW cm(-2)), and the Zn nanowires subsequently act as effective electron collectors, resulting in an extremely high photocurrent under an Ohmic contact electrode. The photoelectric current of the composite ZnSnO3 nanowires exhibited a rapid photoresponse of similar to 1 sec upon irradiation by UV light. An extremely high photo-current to dark-current ratio is 2.7 x 10(5)%. The composite nanowires exhibited an extremely high photodegradation ratio of similar to 66% within 30 minutes under UV-light irradiation. Photocatalysts of composite ZnSnO3 nanowires were found to be superior to those made from composite ZnO-SnO2, ZnO, and SnO2 nanowires. The ZnSnO3 nanowires successfully acted as key components of the photoexcited separation and migration of the generated charges with a low recombination rate. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.053205jes] All rights reserved.