Medulloblastoma is a malignant invasive embryonal tumor of the cerebellum with preferential manifestation in children. The peak of occurrence is seven years of age Seventy percent of medulloblastomas occur in individuals Younger than 16. In adulthood, 80% of medulloblastomas arise in the 21-40 years age group. A 48-year-old male patient was admitted to the hospital with complains of headache, ataxia, morning vomitting and difficulty in speech was operated with the diagnosis of presence of mass of 4 x 7 cm size retaining a diffuse homogenous contrast in the posterior fossa. The diagnosis of desmoplastic medulloblastoma was given after histopathological examination. Immunohistochemical examination revealed that neoplastic cells showed staining with neuron-specific enolase and synaptophysin but not with glial fibrillary acidic protein. This lesion showed nodular, reticulin free-zones (pale islands) surrounded by densely packed, highly, proliferative cells. The pale regions within the tumor did not contain retictifin fibers. Desmoplastic medulloblastoma is encountered especially in adulthood. This type of tumor rarely occurs beyond the fifth decade of life. We present a case of desmoplastic medulloblastoma in a 48-year-old male. - desmoplastic medulloblastoma; adulthood; posterior fossa (C) 2004 Tohoku University Medical Press.