Ependymomas are neoplasms which, on the one hand, supply useful morphological findings that help to make the diagnosis, and, on the other, do not provide certain elements for a reliable prognosis. The difficulties related to the neoplasm topography, the type of surgery and other clinical-operational problems can be overcome, whereas those arising from the limitations of descriptive morphology remain insurmountable since the latter does not supply precise predictive information concerning such a histotype. The Authors have re-examined the issue by studying 31 cases of benign ependymomas and by applying to them static cytometry on Feulgen stained samples. The results obtained (see the histograms enclosed) have revealed the presence of heterogeneous cell clones with polyploid and hyperploid cell populations. These cell populations, though a minority and often also marginal, represent the starting point not only of real recurrence, but also of malignant transformations. The cytometric method has analytically revealed a composite cytologic reality of which the common histological methods can only provide approximate, unreliable and subjective evaluations.