SummaryA case of acute influenzal meningo-encephalitis is described. Its influenzal origin was demonstrated serologically. The psychic symptomatology was very peculiar and could be divided into three stages : ambulatory automatism, excito-subconfusion, maniac episode. The neurologic and meningeal signs are discrete and transient. The clinical evolution suggests a cerebral lesion directly due to the neurotropic influenza virus. The psychic symptomatology, the fugacity of the meningeal and neurologic signs and the spontaneous cure without sequellae depict the benignity of the case.