A patient was treated for symptoms of toxic psychosis, a form of organic brain syndrome, induced by tetanus antitoxin; her personal history showed an unstable emotional background, plus immediate emotional stress, prior to the onset of the overt psychotic behavior. The resultant lack of conviction about diagnosis and etiology led to other considerations, including pathology and treatment. Review of the pertinent literature revealed: 1. Support for the influence of pre-morbid background on the nature of toxic reactions; 2. The absence of any case of toxic psychosis caused by tetanus antitoxin; and 3. Evidence indicating the role of situational stress in the production of so-called toxic reactions.The conclusions reached were that a close scrutiny is indicated in the toxic psychoses before the application of such a diagnosis, and further scientific investigation into the "organic" nature of this disorder seems warranted.