Many years of observation on a considerable amount of clinical material have convinced us that exogenous infection (i. e., exposure to other patients in active phases of the disease) has played no role in the production of attacks of ringworm of the feet and groins in our patients. On the contrary, almost all of our adult patients can at all times be shown to carry the pathogenic fungi in quiescent foci on the feet, toe nails or groins, but they have exacerbations of common forms of "ringworm" only when certain contributory or trigger factors lower their resistance to their own germs. We now, therefore, tell our patients with the common forms of fungous infections of the groins and feet that the disease is rarely, if ever, "contagious" for other members of the family or household, and we abstain from giving directions for the protection of others and confine our efforts