Indium nitride thin films have been deposited using reactive rf-magnetron sputtering and characterized by their electrical, structural and morphological properties. Films have been prepared on fused quartz and (0001) sapphire. Films deposited on sapphire at temperatures from 50–300°C are typified by a slowly increasing mobility and a transition from mixtures of epitaxial and textured grains to complete epitaxy. Comparisons of films deposited on quartz and sapphire (with two different surface preparations) indicates that electrical mobility is enhanced by the epitaxial nature of the material deposited on sapphire and that a higher quality surface finish results in superior films. Somewhat above 300°C the morphology of the epitaxial films changes from continuous to granular, with a concomitant loss in electrical connectivity. This manifests itself as a sharp rise in the resistivity of the film and hence a sharp decline in the mobility. The carrier concentration shows a general decline as the substrate temperature is increased, indicating that the mechanism of mobility degradation is probably not due to thermally induced nitrogen vacancy formation but more likely to unintentional oxygen doping. This is in accord with the surface oxidation observed in the films using Auger electron spectroscopy.