Astrocytomas of the cerebellum are unusual among the gliomas of the brain. They differ materially, not only in symptomatology, but in operability, clinical course, and prognosis from astrocytomas of the cerebrum. They occur predominantly though not exclusively in children. They are usually associated with large cysts filled with a xanthochromic fluid of high protein content. They often arise within and destroy the vermis, while producing a cyst which involves one hemisphere of the cerebellum, thus giving rise to predominantly unilateral clinical manifestations of cerebellar dysfunction. These cysts are almost always outside of the tumor itself, the latter occupying only a small portion of the wall—the so-called mural nodule, although it should be noted that the solid mass of tumor is usually much larger than the word “nodule” would indicate. The remainder of the cystic wall is formed by compressed, sclerotic, non-neoplastic cerebellar tissue. Entirely solid tumors, unassociated with any cyst, are not uncommon. Whether solid or partially cystic, these tumors, in striking contrast with the majority of the astrocytomas of the cerebrum and neural axis, are relatively circumscribed, only moderately invasive, but not encapsulated. They are usually readily extirpated, apparently in toto , although in a considerable number of cases minute microscopic nodules of tumor must be left by the surgeon. Nevertheless, in every case , in our experience, where the surgeon has believed that a complete extirpation of the tumor has been made the patient has subsequently recovered and to date shown no evidence of recurrence (Bailey, Buchanan and Bucy, 5). Cushing (15) in an extensive experience with 76 cases over a period of many years had a similar result. Ford (18) has recently regarded these tumors much more pessimistically and expressed the opinion that all ultimately recur. It can only be concluded that in his cases incomplete extirpations were made. Recurrence is the usual experience after a known incomplete extirpation, as is borne out by Cushing's experience and by ours. The period between the initial operation and the recurrence is variable but always a matter of years. In one of Cushing's cases (No. 5) eleven years elapsed between evacuation of the cyst in 1911 and the recurrence of symptoms necessitating aspiration in 1922, and two more before extirpation of the tumor in 1924. In one of our cases the cyst was evacuated in 1930 and, because of the precarious condition of the patient, no attempt to remove the solid tumor was made. This boy is still alive and well without any evidence of recurrence over eight years later. Hausman and Stevenson (19) reported a case (the only one in the literature to our knowledge, although we have seen a similar case in which the tumor was a teratoid cyst) in which the relatively acute symptoms led to the diagnosis of a cerebellar tumor by Allen Starr. No treatment was undertaken. The symptoms subsided and at a necropsy examination many years later the presence of a cerebellar tumor was confirmed. The tumor proved to be a cystic astrocytoma.