The paper reviews the origin of bright and dark Electron-Beam-Induced Current (EBIC) contrast due to extended defects in silicon, inclusively a brief discussion of contrast modelling. Particular emphasis is put on the role of impurities demonstrated to determine contrast in many cases (extrinsic contrast origin). The understanding of the prevalent contrast type -dark contrast due to enhanced recombination at defects -is well supported by existing phenomenological contrast models which can, therefore, be used as a basis for contrast interpretation. In the context of extrinsic vs. intrinsic contrast origin, the influence of defect dimensionality on contrast is addressed, indicating that grain boundaries of even low recombination activity might produce detectable contrast, in contradiction to dislocations and point-like defects. It is shown that transition-metal precipitates are very efficient recombination sites and that their activity is in accordance with the existence of internal Schottky barriers