Mechanical properties and deformation behaviour of ice in the huge polar ice masses control the internal flow of ice sheets and material supply towards the oceans. The flow behaviour of the material is in turn depending on the microstructure, that is the grain and subgrain morphology and crystal and subcrystal orientations. We present data obtained with classical optical microscopy on grain size and shape, as well as novel results from comprehensive combinations of light microscopy (LM microstructure mapping ^1) and full-crystal orientation measurements (X-ray Laue diffraction ^2 and Electron backscattered diffraction ^3). These data provide insight into activity of recrystallization processes caused by deformation, e. g. strain induced grain boundary migration, but also into the activity of different dislocation types. High-resolution measurements of lattice distortions across subgrain boundaries localized and pre-characterized by optical means, reveal characteristic configurations, which can be interpreted in terms of dislocation activity. The peculiar nature of dislocations in hexagonal ice leads to a limited number of stable dislocation wall configurations. ^1 Weikusat, I.; Kipfstuhl, S.; Faria, S. H.; Azuma, N. \& Miyamoto, A. Subgrain boundaries and related microstructural features in EPICA-Dronning Maud Land (EDML) deep ice core. J. Glaciol., 2009, 55, 461-472, doi: 10.3189/002214309788816614 ^2 Weikusat, I.; Miyamoto, A.; Faria, S. H.; Kipfstuhl, S.; Azuma, N. \& Hondoh, T. Subgrain boundaries in Antarctic ice quantified by X-ray Laue diffraction. J. Glaciol., 2011, 57, 85-94 ^3 Weikusat, I.; de Winter, D. A. M.; Pennock, G. M.; Hayles, M.; Schneijdenberg, C. T. W. M. & Drury, M. R. Cryogenic EBSD on ice: preserving a stable surface in a low pressure SEM. J. Microsc., 2010, doi: 10.1111/j.1365-2818.2010.03471.x