1 Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Key Biscayne, FL 33149, USA 2 Centraalbureau voor Schimmelcultures, Oosterstraat 1, 3742 SK Baarn, The Netherlands 3 Centraalbureau voor Schimmelcultures, Yeast Division, Julianalaan 67, 2628 BC Delft, The Netherlands Author for corresondence: Jack W. Fel. Tel: +1 305 361 4603. Fax: +1 305 361 4600. e-mail: jfell{at}rsmas.miami.edu ABSTRACT The order Cystofilobasidiales is described for teleomorphic basidiomycetous yeasts with holobasidia and teliospores. Their septa have dolipores, but lack parenthesomes. D-Glucuronate, nitrate and nitrite are assimilated and myo inositol is usually assimilated. Coenzyme Q has 8 or 10 isoprenologues. 25S and 18S rDNA sequence analysis indicates a monophyletic branch within the Tremellomycetidae of the Hymenomycetes. Cystofilobasidium is the type genus. Key Words: phylogeny • basidiomycetes • yeast • rDNA • Cystofilobasidiales The GenBank accession numbers for the sequences reported in this paper are AF075463 --AF075526.