Abstract: A list is given of 305 specimens (126 species) of ‘microfungi’ (Peronosporales, Uredinales, Ustilaginales, Ascomycetes, Fungi lmperfecti etc.) collected by the author between November 1969 and June 1970, mainly in southern Argentina and central Chile. The majority of species have cosmopolitan or bipolar distributions or are known to be typical and frequent in southern South America. Additions to the geographical distribution and notes on the abundance of infection are given for a considerable number of species insufficiently studied up to now. Many previous discoveries are confirmed, especially from the region of Ushuaia, Tierra del Fuego. The following new taxa are described: Peronospora ranunculi-peduncularis Roiv. on Ranunculus peduncularis Smith, P. ranunculi-peduncularis var. ranunculiminutiflori Roiv. on Ranunculus minutiflorus Smith, Urocystis permagna Roiv. on Poa cf. oligeria Steudel, Septaria gregoria Roiv. on Adesmia campestris (Rendle) Rowl., Phleospora aenigmatica Roiv. on Gentianella magellanica (Gaud.) Fabris ex D. M. Moore, Anthracoidea Ortegae Kukkonen on Carex Ortegae Phil., and Cintractia andina Kukkonen on Schoenus andinus (Phil.) Pfeiffer.