A working concept of the multiple processes involved in chronic paronychia is presented. In experimental studies, rounding out and retraction of the posterior nail fold occurred when the fingers were inoculated with C albicans and occluded for 30 days. No attempt was made to control secondary invaders in the six lesions which developed the morphologic changes typical of chronic paronychia. On the basis of the multiple studies presented in this paper we feel that the rounding out and retraction phenomenon is most likely the result of the passage of foreign material into the dermis. Severe maceration and inflammation destroy the normal epidermal barrier. The foreign material probably arises from the organisms of the fold.