Large-scale, ultralong CdS nanowires (NWs) were grown by a simple thermal evaporation process. The NWs have diameter of 100-500 nm and lengths up to 1 mm. A Sn-catalytic vapor-liquid-solid mechanism is proposed to explain the growth process. The optical waveguide behavior of both individual NW and multi-NWs interconnected structures have been investigated, which indicates that the as-prepared CdS NWs are good optical waveguide material and may find potential applications in nano-photonic devices or systems. (C) 2010 Elsevier B.V. All rights reserved.