The orientation taken by a bulk nematic liquid crystal in contact with a substrate can vary with certain parameters, leading to anchoring transitions. Such bulk reorientations are the result of structural transitions taking place in the region of the liquid crystal close to the substrate—the interfacial region—which are driven by the molecules located at the substrate surface. Starting from the experimentally measured orientational distribution of these molecules, it is possible to predict correctly the orientational behaviour of the rest of the liquid crystal and in particular the anchoring transitions.