Medulloblastoma/primitive neuroectodermal tumor (PNET) is an uncommon tumor in adults. We reviewed the medical records of 45 patients, 15 years or older, with medulloblastoma/PNET. Most patients presented with symptoms referable to the posterior fossa, and 31 of 45 patients had disease limited to the posterior fossa at the time of diagnosis. Despite initial favorable response to surgical resection, radiation, and chemotherapy, one-half had recurrence 10 to 76 months after initial treatment. Only two of these patients had local recurrence; the remainder had CNS dissemination, systemic metastasis, or both. The recommended approach to medulloblastoma/PNET in adults is similar to that in children, and includes initial staging evaluation, systemic and focal therapy (ie, neuraxis irradiation with posterior fossa boost and chemotherapy), and long-term follow-up to detect late and distant recurrence.