The authors study the mycosis produced principally by microsiphonades in man and animals, in the State of Minas Gerais. The following species are studied: I - "Actinomyces bovis". II - "Actinomyces brasiliensis". III - "Proactinomyces asteroides var. decolor". They also describe a case of foot-mycetoma (Madura-foot) by "Monosporium apiospermum" and two cases of pseudo mycetoma: The first, on the cheeck, by "Rhinocladium Beurmanni" and the second, on teh arms, by calcium salts. They relate the fundamental notions on actinomicotic granules and describe the cultural properties of the species. They give a summary of clinical observations with their respective origins.