Among the open questions regarding the rodent whisker-dependent behaviors, an important aspect is undoubtedly represented by the way the rat brain processes signals generated by the active movements of the whiskers to extract a real image of the surroundings. Contact between whiskers and objects produces time-varying stresses at the base of the macrovibrissae that are transduced into action potentials by mechanoreceptors of the follicles and relayed to the CNS by the trigeminal nerve. However, it has been recently demonstrated that besides the trigeminal ganglia even the trigeminal mesencephalic nucleus is involved in detecting kinetic information from macrovibrissae receptors. Spontaneous and artificial movements of whisker pad macrovibrissae elicit in fact evoked responses in the trigeminal mesencephalic nucleus (Me5). Besides that, neuroanatomical procedures showed that the Me5-macrovibrissae neurons are localized in the medial-caudal part of the nucleus and have their peripheral terminals coiled around the macrovibrissae shaft [Mameli et al. 2010, 2014]. The present study was aimedat understanding whether or not within the Me5-nucleus a neuroanatomicalrepresentation of the whisker pad macrovibrissaeexists. The experiments were performed on different groups of anaesthetized Wistar rats, (diazepam 30 mg/kg, ketamine hydrochloride 45 mg/kg),which were submitted to a tracer injection in selected points of the whisker pad. In animals of group 1 only a single macrovibrissae was injected, in group 2 five macrovibrissae along a single row, in group 3 the stradler whiskers (i.e. the vibrissae α, ß, γ, δ). Finally, in group 4 the whole whisker pad was uniformly labeled. Fluorescent histological analysis wasperformed by Confocal Microscopyto detect the Me5 neurons labeled by Dil. Results showed thatthe whisker pad macrovibrissae are represented at the levelof the nucleusmedial-caudal part, and that the Me5 labeled neurons were globular, oval or triangular in shape. They had variable sizes (30-55 µm) and were provided with two or multiple processes that could be followed for some distance. Moreover, it has been demonstrated that they are clustered in arrays of cellular aggregates, which althoughdid not correlate with the geometrical architecture of the macrovibrissae onto the whisker pad, did resemble thespecial arrangement of other trigeminal neurons within their relay stations. Finally, since the number of the labelled neurons matched that of the macrovibrissae, thisdata raises the question as to whether such correlation is related to a specific functional role of single Me5 macrovibrissae-neurons. Specific electrophysiological experiments will be therefore needed to address this issue.