Diffuse low grade gliomas (DLGG) are continuously progressive primary brain neoplasms that lead to neurological deficits and death. Treatment strategies are controversial. Randomized trials establishing the prognostic value of surgery do not exist. Here, we report the results of a nine-year near-randomized patient distribution between resection and biopsy. Until 2012, the Department of Neurosurgery and the Department of Stereotactic Neurosurgery at the University Medical Center Freiburg were organized as separate administrative units both coordinating DLGG patient treatment independently. All consecutive adult patients with a new diagnosis of DLGG by either stereotactic biopsy or resection were included. Pre- and post-operative tumor volumetry was performed. 126 patients, 87 men (69%), 39 women (31%), median age 41 years, were included. 77 (61%) were initially managed by biopsy, 49 (39%) by resection. A significant survival benefit was found for patients with an initial management by resection (5-year OS 82% vs. 54%). The survival benefit of patients with initial resection was reserved to patients with a residual tumor volume of less than 15 cm3. Maximum safe resection is the first therapy of choice in DLGG patients if a near-complete tumor removal can be achieved. Accurate prediction of the extent-of-resection is required for selection of surgical candidates.