LANGERON1 has stated the belief that knowledge of the epidermomycoses with black pigmentation is still imperfect, for two reasons. The first is nomenclature, as the same disease has received different names according to the different countries and the several observers connected with the study of this morbid condition. It is also an undoubted fact that the same name has been given indiscriminately to different diseases. The second factor responsible for the prevailing confusion is that the fungi which cause this epidermomycosis are mostly unknown or imperfectly known, for they have not been carefully studied. For these reasons we have resolved to make the fullest possible study of this mycosis both from the anatomoclinical point of view and from the mycologic standpoint of its causal agent. DEFINITION Tinea nigra is a contagious, inoculable and autoinoculable dermatomycosis which is caused by two fungi, Cladosporium mansoni and Cladosporium wernecki. It is characterized,