Present evidence supports the original view of the medulloblast as a bipo-tential cell with the capacity for differentiation along either spongioblastic or neuro-blastic lines. Medulloblastomas behave much like other tumors of presumed embryonal origin, and in this respect the period describing risk of recurrence after treatment follows Collins’ rule of age at the time of treatment plus nine months. Always regarded as highly radiosensitive, medulloblastomas now emerge as radio-curable with almost one-third of postoperative patients surviving ten years beyond radiation therapy. Clinical trials have shown the sensitivity of medulloblastomas to two oncolytic drugs, methotrexate and vincristine. The rationale behind intermittent intrathecal administration of methotrexate is presented in the light of present knowledge. In the future, chemotherapy will assume an increasingly important role in the treatment of medulloblastomas resisting cure by irradiation.