Castellani1 first named and described dermatosis papulosa nigra in a brief note, and later, in collaboration with Duval,2 expanded his original clinical report and included a brief pathologic study. For several years this dermatosis has attracted our attention, and during that time we have collected some observations of it which form the basis of this paper. In the main, we have been interested in its incidence, pathologic changes and nosologic position, but before proceeding to these phases of the subject, we shall describe its clinical features as a review and amplification of Castellani's observations. SYMPTOMATOLOGY AND INCIDENCE The disorder occurs almost exclusively among negroes; we have seen it once in a Mexican of the peon class, while Castellani saw it in a European. We noted that the disorder may appear in childhood, as early as the seventh year. At this age, minute, round, semiglobular papules, skin colored or