ABSTRACTComparisons of nuclear DNA complementarity were used to determine the extent of genetic relatedness between phenotypically similar species ofPichia.Pichia xylosa, a presumed synonym ofP. toletana, proved to be a distinct but closely related species.P. guilliermondiiandCandida guilliermondiiwere confirmed as a teleomorph/anamorph pair.Hansenula ukrainicawas shown to be conspecific withP.(H.)anomalaandP. cellobiosato be conspecific withP. methanolica.