A yeast strain isolated from the air in Japan was found to represent a new species, and was named Trichosporon japonicum. This species produced arthroconidia and appressoria. T. japonicum formed a cluster with the appressorium-forming species Trichosporon inkin and Trichosporon ovoides in a phylogenetic tree constructed using small-subunit rDNA sequences. However, they had low relatedness to each other in DNA-DNA hybridization experiments. T. japonicum is distinguished from both T. inkin and T. ovoides by its ability to assimilate inulin, and its inability to assimilate L-rhamnose. JCM 8357T is the type strain of the species.