The prime purpose of this communication is to analyze the psychotic features of epidemic encephalitis as they have been observed in a group of twenty-three cases admitted to the Henry Phipps Psychiatric Clinic of the Johns Hopkins Hospital, between the spring of 1919 and the summer of 1920. It also seems worth while to report the cases in some detail and briefly to analyze them from other points of view, because they are so protean. In practically all instances these cases were referred to the clinic because of mental symptoms or behavior difficulties. It is, of course, not supposed that mental symptoms play as important a rôle in the disease picture as this group would indicate. The cases were selected for us, as it were, from the larger group which, for the most part, was admitted to the general hospital. On the other hand, this series does not constitute a