The therapy for medulloblastoma/primitive neuroectodermal tumors of the central nervous system is surgery, followed by combination chemo-radiotherapy. The radiation field is the entire craniospinal axis, which is only avoided when treating infants. The treatment is, therefore, lengthy and toxic. Less aggressive therapy is given to patients who clinically appear to have less evidence of disease. Intensive basic research has begun to identify genetic factors of the disease, but these remain far from clinical application.