We describe a patient with acute disseminated encephalomyelitis (ADEM) who was treated with high-dose intravenous methylprednisolone 2 days after onset of neurologic symptoms. Despite poor prognostic factors and extensive white matter lesions, the patient recovered dramatically with no need for maintenance steroid therapy. This case report of fulminant ADEM treated successfully with early high-dose intravenous methylprednisolone, although uncontrolled, suggests that this agent should be studied in other cases.