Phylogenetic analysis of Eucalyptus subgenus 'Eudesmia' is presented on the basis of the following three datasets: sequences of the internal transcribed spacer (ITS) and the external transcribed spacer (ETS) regions from nuclear rDNA, sequences of the psbA–trnHintergenic spacer region from chloroplastDNA,and morphological characters, including stamen bundling, operculum development, seeds and trichomes. Studies of floral development were essential for understanding the morphology of mature flowers and interpretation of synapomorphy and homoplasy. A summary phylogeny was constructed from a maximum parsimony analysis of those nodes coded as characters that had support in the molecular trees together with morphological characters. A revised infra-subgeneric classification is presented on the basis of the summary phylogeny, and compared with classifications of Hill and Johnson (1998) and Brooker (2000). Differences relate to relationships between clades and taxonomic rank (sections, series and subseries) and valid names of Brooker (2000) are conserved where possible. One main clade of 14 species (section Limbatae), many of mallee growth form, was found in all analyses; this clade is distributed in the South-West of Western Australia and adjacent Interzone and desert areas. A second main clade (section Complanatae) occurs in the northern and eastern tropical and subtropical regions of Australia, including Kimberley, Arnhem, Queensland and NewSouth Wales. This section includes 'E. tetrodonta', previously treated as an isolated taxon in a monotypic section; however, this species is related to 'E. baileyana', 'E. similis', 'E. lirata' and series 'Miniatae'. The hypothesised phylogeny provides a framework for further analyses of biogeography and ecology, including functional traits.