In our clinical study of diphtheria of the skin we have limited ourselves to an analysis of the particular phase known as "secondary diphtheria" or "wound diphtheria." There is considerable controversy about this type because it is difficult to determine the exact role of the diphtheria organism. This confusing condition must be differentiated from the many forms of acute and chronic primary diphtheria of the skin. In the primary form, the bacterial flora of the lesion is predominantly, or entirely, diphtheritic even from the onset; cure is obtained by administration of antitoxin, and true postdiphtheritic visceral complications may occur. In the secondary form, the cutaneous lesion is not initiated by the diphtheria organisms, which are found usually by chance or in epidemic surveys; the value of antitoxin is doubtful, and complications are rare. It is possible that the secondary form is commoner than one supposes, but routine bacteriologic surveys of