It has been generally accepted that mature neurons of the central nervous system of adult mammals are incapable of cell-division. Nevertheless, recent data are suggesting the contrary. Mature neurons, bi- or multinucleated, observed in the central nervous system of vertebrates, mammals and man are being differently interpreted: as a result of mitotic or amitotic cell-division of mature neurons; as indiferentiated cells which could indicate a regeneration process; as a cellular reaction to nervous injuries; as the result of the fusion between two mononucleated elements. The cells of the human nucleus n. hypoglossi were counted an studied in 26 white males, the youngest four months old, the eldest, eightysix years old. The material secured at the necropsy table was selected in order to exclude diseases or physical conditions which could interfere with the final results. The medulla oblongata were formalin fixed, imbedded in celloidin, 30µ serial cross sectioned, numbered and stained by Pal-Weigert modified by Erhart method for myelin sheaths. The counterstain was by carmin. The cells were counted when their cell-bodies showed evident nucleus and nucleolus. They were measured and carefully analysed including with high magnification. From the 202.910 counted cells, 33 were binucleated. These latter did not present any characteristic of mitotic or amitotic cell-division an no relation between age and higher frequency of binucleated cells could be observed. The general morphology of the binucleated cells was equivalent to the mononucleated ones although the former were significantly larger than the latter. The statistical analysis was made by comparision of sample mean of two populations at the five per cent level of significance. It is concluded, considering the studied material and the current literature, that there is no reason to accept, the presence of binucleated nerve cells as a biological reaction due to old age. The real significance of these cells is still unknown, but it can be admitted that they should have a biological capacity which would be qualitatively the same in the differente ages. Nevertheless, their quantitative evaluation is not possible, as far as we know.