Single-crystalline In2O3 nanowires have been synthesized using a laser ablation approach. Precise control over the nanowire diameter was achieved by using monodispersed gold clusters as the catalyst. Extensive material characterization has been carried out to determine the lattice structure (see Figure) and dimensions of these nanowires. Individual In2O3 nanowires have been utilized to construct field-effect transistors with on/off ratios up to 1000.