The question of immunity in ringworm infections has received but scant attention in America. It appears that, until recently, many of the mycologic and biologic problems of the ringworm flora of America have been neglected. Although ringworm infections are not as a rule serious conditions, yet they are often troublesome and besides form a considerable proportion of cutaneous diseases, particularly in the tropics. On first glance, it might appear that the studies herein reported are largely of academic interest, but several particularly interesting clinical problems are involved. Can a simple method be devised for immunizing children, in a family or in institutions, against ringworm? Can a biologic test be devised enabling the differentiation between real palmar and plantar ringworm and the inflammatory conditions that closely resemble ringworm, occurring on these parts, in which either no mycelia are found or in which, if mycelia are found, their pathogenicity is