We report about two female inpatients aged 58 and 24, suffering from non-purulent meningoencephalitis, in the first case caused by varizella-zoster-virus, in the second case probably due to viral infection. Both patients developed a diffuse brain edema associated with a progressive loss of consciousness. The adjunctive treatment with dexamethasone led to rapid improvement of clinical symptoms. Computed tomography revealed a significant reduction of brain edema. These results of these two cases support the efficacy of corticosteroids as adjunctive treatment of diffuse brain edema caused by non-purulent meningoencephalitis. The pathophysiological mechanisms are discussed.