In this study, indium tin oxide (ITO) thin film was evaporated on Mg-doped p-GaN layers with low 10(17)/cm(3), grown by metalorganic chemical vapor deposition (MOCVD) on (0001) sapphire wafers, and its contact properties were investigated. The sheet resistance (Rs) of the evaporated ITO films was several k Omega/rectangle before the annealing but the sheet resistance decreased to 40-50 Omega /rectangle after the annealing in N-2 using a rapid thermal annealing (RTA) system. I-V characteristics and contact resistivities of the evaporated ITO on p-type GaN were investigated as a function of substrate treatment, annealing time, and annealing temperature. The results showed that, in optimized conditions, the ITO contacts with the resistance in the range of low 10(-1) SZ cm(2) could be obtained, and which is probably applicable as the ohmic contact for GaN-based light emitting diodes. Also, at these conditions, the measured optical transmittances of ITO film were above 90% at a wavelength of 420 nm. (blue).