The purpose of this article is to report a case, clinically diagnosed as encephalitis lethargica, verified by observations antemortem and postmortem. As a result of the influenza epidemic which raged in Southern and Middle Europe in 1890, cases of epidemic lethargy appeared in Italy and in Hungary.1Economo,2writing about an epidemic which occurred in Vienna in 1917, likewise speaks of these cases, which at the time were called "nona." He introduced the term encephalitis lethargica. Wilson3gives a description of the pathologic changes in the brain of cases of this disease and ascribes the cause to a toxi-infective origin. Von Weissner, as mentioned in the special article on lethargic encephalitis inThe Journal of the American Medical Association, March 15, 1919, recovered a gram-positive diplostreptococcus which he claims produced somnolence when injected into apes. Up to the present time, however, no organism has been described which