In this paper, we describe the technique of electron backscattered diffraction (EBSD) and illustrate its use in the characterisation of nitride thin films by describing our results from a silicon-doped 3 μm thick GaN epilayer grown on a sapphire substrate misoriented by 10 o towards the m-plane (10-10). We show that the EBSD technique may be used to reveal the relative orientation of an epilayer with respect to its substrate (a 90 o rotation between the GaN epilayer and sapphire substrate is observed) and to determine its tilt (the GaN epilayer was found to be tilted by 12+/-3 o towards [10-10] G a N ).