Plane strain channel die compression (PSC) deformation has been carried out on Al-Mg alloys with Mg contents of 0.1 to 5% at 350degreesC, and the deformed microstructures characterised by channelling contrast backscattered electron imaging (BSE), secondary electron imaging (SE) and high resolution electron backscatter diffraction (EBSD). Measurements of orientation spread and misorientation gradient obtained from EBSD maps have been used to quantify the microstructural inhomogeneity developing in the 4.98% Mg alloy. The results are consistent with inhomogeneous plasticity with more deformation occurring in the grain boundary regions. In-situ FEGSEM hot deformation experiments on the Al-4.98% Mg alloy have provided evidence of stress driven boundary migration at low strains.