One of the problems connected to the anatomo-clinical evaluation of ependymomas consist in the difficulty of precisely grading these neoplasms and of making a prognosis. Traditional histopathologic procedures have proven themselves unsuitable to solve these biological problems of neoplastic growth: their solution requires the identification and responsiveness of molecules that are part of cellular kinetic processes such as antigen Ki67 and the granules of AgNOR as indexes of the rDNA transcriptional activity. With the aim of contributing to the knowledge of ependymomas' grading, the Authors performed qualitative and quantitative assays on 35 cases of benign ependymomas (by means of an image analyzer) using the nuclear antigen Ki67 and the AgNOR nucleolar areas. The results thus obtained allow to draw the following conclusions: 1) The biological validity of the labeling of antigen Ki67 and the quantification of argentophilic granules in the NOR areas has once more been confirmed. 2) The expressiveness and biological significance of antigen Ki67 is finer than what can be derived from the count of AgNOR granules. 3) The level of diagnostic reliability for the differentiation between and the corresponding malignant forms is optimal; such a level falls considerably when one wishes to grade levels of benignity of malignity. 4) Such drawbacks are likely to be due to the action of heterogeneous factors which are often unrelated to the neoplasm, such as poor oxygenation, blood stream alterations, necrosis, phlogosis, nutritional conditions of the cell populations etc.