In previous communications from this clinic, it has been pointed out that the true tumors of the central nervous system represent about 40 per cent, of all intracranial neoplasms. Considered as a group, these lesions usually receive the pathologic diagnosis of glioma; this unqualified term implies to many a condition of hopeless malignancy. However, the fact has gradually become appreciated that certain types of glioma are favorable to operative removal and others are favorably influenced by radiation. It consequently is important, more especially for the neurosurgeon, on both prognostic as well as therapeutic grounds, that his clinical experiences should be correlated with a more detailed classification of the gliomas than is customary. This is a task the authors have set for themselves,1and in the course of a preliminary survey of the material at hand, representing the records and tissues of approximately 400 gliomas, we were impressed by the