In this project, the phylogenetic relationships of tribe Epidendreae, especiallysubtribe Laeliinae were assessed by using DNA sequence data. At the tribal level, Iused data from three DNA regions, namely internal transcribed spacers of nuclearribosomal DNA (ITS), and plastid matK (gene and spacers) and trnL-F (intron, exonand spacer). After individual and combined phylogenetic analysis using parsimony, itwas possible to delimit Epidendreae as an exclusively Neotropical tribe (composedof subtribes Laeliinae, Pleurothallidinae, Ponerinae, Bletiinae and Chysinae). It isstill unclear whether Coeliinae and Calypsoeae should be also included inEpidendreae. All Old World subtribes placed in Epidendreae in Dressler’s (1993)system belong to different tribes of subfamily Epidendroideae. The revised subtribeBletiinae is composed only of Bletia, Hexalectris and Basiphyllaea. All Old Worldgenera previously placed in Bletiinae belong also to Old World groups. Arpophyllum(previously Arpophyllinae) and Meiracyllium (previously Meiracyllinae) should beincluded in Laeliinae. Neocogniauxia and Dilomilis belong to a clade sister toPleurothallidinae. Ponera, Isochilus and Helleriella (previously in the Scaphyglottisalliance within Laeliinae) belong to a recircumscribed version of Ponerinae, which issister to Bletiinae. Two other datasets were collected to investigate in more detailphylogenetic relationships within Laeliinae. The first dataset used 295 ITS sequencesto assess generic delimitation and species phylogenies. Because the levels ofvariation were low, there was little resolution along the spine of the tree, and fewgeneric groups achieved strong internal support. However, most species groupsobtained were coincident with previous taxonomic groups at the infrageneric level,but several genera were found to be polyphyletic, including Cattleya, Laelia,Encyclia, and Schomburgkia. A second analysis of Laeliinae used the same threegene regions as in the Epidendreae study. This analysis found increased support forgeneric groups, confirmed polyphyly of several genera, and clarified unusualrelationships in the ITS study. It also confirmed the suspicion that some ITSsequences were paralogous copies, although the underlying cause of the paralogyremains uncertain. Comparison of the three studies emphasise the importance of bothtaxon and character sampling in phylogenetic reconstruction.