Patients with primary brain tumours often develop vasogenic edema and increased intracranial pressure. Corticosteroid therapy improves this in most patients, generally within 48 hours. As such, corticosteroid therapy is sometimes a necessary prerequisite to embarking on chemotherapy and radiotherapy following surgery, particularly in patients whose brain tumours exert significant mass effect. Similarly, management of edema and intracranial pressure with corticosteroids forms an integral aspect of treatment in the post-radiotherapy phases of care. Dexamethasone is the usual corticosteroid of choice, because of its minimal mineralocorticoid activity, long half-life, and high potency. Despite its common use, however, there have been few prospective clinical trials to determine the optimal dose and schedule for dexamethasone in patients with primary brain tumours, and subsequently fewer clinical practice guideline recommendations. Dexamethasone and all steroids are associated with a variety of side effects, therefore the risks and benefits must be weighed carefully for each patient. The goals of this guideline are to review the evidence for the use of dexamethasone in patients with high-grade gliomas, to describe the management of side effects associated with dexamethasone use in this patient population, and to document the recommendations of the Alberta Provincial CNS Tumour Team for the use of dexamethasone in patients with high-grade gliomas.