Phylogenetic trees of the anamorphic basidiomycetous yeast genus Trichosporon Behrend, based on molecular sequence analysis of the internal transcribed spacer region and the D1/D2 region of the large subunit of ribosomal (26S) DNA, are presented. This study includes three novel species from soils, Trichosporon vadense sp. nov. (type strain, CBS 8901(T)), Trichosporon smithiae sp. nov. (type strain, CBS 8370(T)) and Trichosporon gamsii sp. nov. (type strain, CBS 8245(T)), one novel species from an insect, Trichosporon scarabaeorum sp. nov. (type strain, CBS 5601(T)) and one species of unknown origin, Trichosporon dehoogii sp. nov. (type strain, CBS 8686(T)). The phylogenetic positions and physiological characteristics that distinguish the new taxa from related species, based partly on growth tests that are not traditionally used in yeast taxonomy (uric acid, ethylamine, L-4-hydroxyproline, tyramine and L-phenylalanine as sources of carbon and nitrogen, and polygalacturonate, quinate, 4-ethylphenol, phloroglucinol, 2,3-dihydroxybenzoate and orcinol as sole carbon sources), are discussed. Assimilation of L-rhamnose and erythritol and maximum growth temperature were also used to delineate species.