Two patients with presumed encephalitis lethargica are presented with clinical features suggestive of two forms of the disease described by Von Economo: One patient had a psychosis and a mute-akinetic syndrome associated with myoclonus. The second patient presented with a psychosis and fever, developing severe dyskinesias involving the mouth, trunk and limbs, together with respiratory irregularities and presumed hypothalamic disturbance and disturbance of consciousness. In both cases, initial cerebrospinal fluid (CSF) examination revealed an elevated white cell count (predominantly lymphocytes), elevated protein in case 2, and oligoclonal bands in both cases. Computed tomography (CT) brain scan was normal but in both cases EEG revealed diffuse slow wave activity. A 18F-Dopa positron emission tomography (PET) scan in case 2 was normal. The medical management of both patients is discussed. In case 1, L-Dopa improved the akinesia, while the myoclonus responded to clonazepam. In case 2, the severe dyskinesias failed to respond to a number of drugs, and she ultimately required paralysis to relieve her almost continuous movements. Both patients responded rapidly and dramatically to intravenous methylprednisolone. We suggest that steroid treatment should be considered in the acute phase of patients with features suggestive of encephalitis lethargica.