The four varieties of human infections caused by fungi whose mycelium or conidia or both are dark colored, are described and discussed under the headings of superficial, cutaneous, subcutaneous and systemic mycoses. Three diseases, black piedra, tinea nigra and mycotic keratitis, were considered in the superficial category. Their etiologic agents, respectively 4 and 17 in number were briefly described in terms of their clinical manifestations, in vivo and in vitro morphology. The subcutaneous mycoses with dematiaceous etiologic agents are chromoblastomycosis and phaeohyphomycosis. The former is considered to be caused by any one of six moulds classified in the genera Cladophialophora, Cladosporium, Fonsecaea, Phialophora and Rhinocladiella. The fungi incriminated as agents of phaeohyphomycosis, currently total 32. The fundamental differences between chromoblastomycosis and phaeohyphomycosis lies in the tissue form assumed by their respective etiologic agents. In chromoblastomycosis, the parasites occur as large, muriform, thick-walled dematiaceous cells. In phaeohyphomycosis the fungi basically occur as dark walled septate, hyphal elements. The mycetomas with black granules are known to be caused by 9 species of moulds classified in 6 genera. Within limits, the identity of a given black grained mycetoma can be deduced through the characteristics of the granules.