Chloroquine is a strong lysosomotropic and DNA-intercalating agent in experimental studies (Neurosurgical Focus 14(2): February, 2003) and an open-label clinical trial the investigators have demonstrated a strong adjuvant effect of chloroquine on the therapy of malignant gliomas. This study will assess in a randomized, placebo-controlled, double-blind study the effects of chloroquine as adjuvant to the conventional therapy of Glioblastoma Multiforme.