In the framework of an investigation of the extremophilic biodiversity of Antarctic lake microbial mats, 26 species of filamentous fungi belonging to 15 genera were isolated, in addition to 11 species of yeasts belonging to 6 genera. Species were identified phenetically and by sequencing of the rDNA Internal Transcribed Spacer (ITS) domain. It is concluded that Thelebolus and some basidiomycetous yeasts are probably the only ones which are metabolically active under Antarctic conditions.