ALL the exotoxins except diphtheria toxin have been demonstrated within the bacterial cells in a very early stage of culture. So far as diphtheria toxin is concerned, it has been postulated, but never proved, that the exotoxin is formed within the cell. I have, however, previously deduced the possibility of temporary existence of the toxin within the cell from the morphological and biochemical characteristics of this organism1,2. I believe that the failure to show the presence of the toxin was due to the fact that physiologically young cells of C. diphtheriae, however early they might be harvested, could not be obtained when static culture was used.