Abstract: Ferroptosis (cell death mediated by iron-dependent lipid peroxide accumulation) results from lipid peroxidation of phospholipids containing polyunsaturated fatty acyl moieties. Glutathione, the key cellular antioxidant capable of inhibiting lipid peroxidation via the activity of the enzyme glutathione peroxidase 4 (GPX-4), is generated directly from the sulfur-containing aminoacid cysteine, and indirectly from methionine via the transsulfuration pathway. Cysteine and methionine deprivation (CMD) in the diet can synergistically increase RSL3-mediated cell death and lipid peroxidation in both murine and human glioma cell lines and in ex-vivo organotypic slice cultures. A cysteine-depleted, methionine-restricted diet can improve survival in an syngeneic orthotopic murine glioma model. This CMD diet leads to profound in-vivo metabolomic, proteomic and lipidomic alterations, leading to improvements in the efficacy of ferroptotic therapies in glioma treatment with a non-invasive dietary modification.