The author studies the psychotic encephalitis in the course of dentofocal infection. He exemplifies his work with a personal case. He claims that the infection was no more than the precipitating factor. There were other causes which had prepared the ground beforehand: moral shock, previous grippal infection, a long period of continuous and intensive work; besides, there was a genotypic charge. The occurring acute confusional syndrome was complicated with total right hemiplegia a few days later. The opening of a large abscess in the left superior gingivo-labialis space and the removal of the damaged tooth (second left superior premolar) with intensive therapeutic measures against the infectious state brought up rapid improvement of the patient, with practically complete psychical recovery. The hemiplegia has completely disappeared, leaving no motor deficiency. The patient had a psychopathic fatherly uncle; one of his brothers had probaly presented a psychopathic personality and it seems that the other has shown mental disorders following a frontal sinusitis. Even the case reported by the author has presented, twelve years ago, similar disturbances following a grippal infection. Concluding his article, the autor studies the focal infections in general. He devotes especial attention to the question of focal infections in Neuropsychiatry, emphasizing the more interesting points of the problem.