Gliomas are tumors of the support cells of the brain and the most common of the primary brain tumors. Treatment of diffuse gliomas is based on surgical excision of the tumor and on radiotherapy and chemotherapy. The diagnosis is made in histopathological examination of the tumor, which today can be complemented with examinations involving molecular diagnostics. The most important new methods predicting the prognosis of glioma patients include demonstrations of the IDH mutation and the 1p/19q co-deletion. Profiling of gliomas may in the future allow tailoring of therapy in a patient-specific manner.