The trial is designed as a multicenter randomized controlled study. 246 patients with presumed Glioblastoma Multiforme in eloquent areas on diagnostic MRI will be selected by the neurosurgeons according the eligibility criteria (see under). After written informed consent is obtained, the patient will be randomized for an awake craniotomy (AC) (+/-123 patients) or craniotomy under general anesthesia (GA) (+/-123 patients), with 1:1 allocation ratio. Under GA the amount of resection of the tumour has to be performed within safe margins as judged by the surgeon during surgery. The second group will be operated with an awake craniotomy procedure where the resection boundaries for motor or language functions will be identified by direct cortical and subcortical stimulation. After surgery, the diagnosis of GBM will have to be histologically confirmed. If GBM is not histologically confirmed, patients will be considered off-study and withdrawn from the study. These patients will be followed-up according to standard practice. Thereafter, patients will receive the standard treatment with concomitant Temozolomide and radiation therapy and standard follow up. Total duration of the study is 5 years. Patient inclusion is expected to take 4 years. Follow-up is 1 year after surgery. Statistical analysis, cost benefit analysis and article writing will take 3 months.