A case of biopsy-proven acute hemorrhagic leukoencephalitis is reported. The early computed tomography scans showed extensive bilateral hypodensities with mass effects and foci of microhemorrhages. Bilateral asymmetric hyperintensities in the mesiotemporal and frontal lobes and massive edema were found on T2-weighted and fluid-attenuated inversion recovery magnetic resonance images in a pattern classic for herpes simplex encephalitis. This fulminant demyelinating disease progresses to coma and death within days. Early diagnosis with neuroimaging studies and rapid correlation with the clinical findings of this disease are vital for the institution of potentially lifesaving treatments.