Encephalitis lethargica, or epidemic encephalitis as it is now usually called, is becoming more generally recognized throughout the world, and while diagnosis is usually easy in those cases with a clear history, and who show the “encephalitic syndrome” to a marked degree, much confusion has arisen in the case of some patients who have shown clinical features which have led observers to arrive at a diagnosis of this disease when later investigations have shown that this conclusion has not been a correct one.