Recent evidence suggests that there are no features that sufficiently distinguish gliomatosis cerebri (GC) from diffuse gliomas. They show the same age and sex distribution, clinical signs, prognostic factors and harbor similar genetic abnormalities. Furthermore, GC can progress secondarily to a higher grade of malignancy. The 2007 WHO classification itemizes GC among astrocytic tumors. Nevertheless, an oligodendroglial differentiation can be observed in up to 40%. These data implicate that treatment guidelines might follow those for diffuse gliomas in general. However, the large extension usually limits surgery to biopsies. The role of whole brain radiotherapy is unclear because no impact on survival could be demonstrated. At least some patients might benefit from chemotherapy (temozolomide).