The electrical behavior of Sn-doped nanocrystalline and microcrystalline TiO2 has been studied by DC conductivity measurements and impedance spectroscopy. Specimens were hot pressed from powders synthesized by a solution chemical method, resulting in highly dense, 100% rutile with an average grain size of similar to 50 nm. Results indicate that nanocrystalline TiO2 has enhanced conductivity relative to microcrystalline TiO2, and a lower specific grain boundary resistivity. The activation energy for conduction in air of both nanocrystalline and microcrystalline TiO2 is lower than values obtained from the literature for polycrystalline and single crystal rutile. Furthermore, conductivity measurements over a range of oxygen partial pressures indicate that the conductivity of nanocrystalline and microcrystalline TiO2 exhibits a P-O2-independent regime that is unique compared to past studies of polycrystalline and single crystal rutile.