The neotropical orchid tribe Maxillarieae includes about 2600 species, roughly 10% of Orchidaceae. We use nrITS and trnL-F sequence data to clarify generic relationships within two problematic subtribes. Zygopetalinae are divided into a prominently-pseudobulbed clade/grade and a largely pseudobulbless clade (Huntleyinae Schltr.) including Dichaea and Cryptarrhena. Chondrorhyncha is polyphyletic; we recognize Chondrorhyncha s.s., Chondroscaphe, Warczewiczella, and several clades that will require generic names. Floral syndromes are homoplasious on the combined trees. Maxillariinae (sensu Dressler 1993) consists of broad Maxillaria (ca. 500 sp.) plus six minor genera (Anthosiphon, Pityphyllum, Mormolyca, Chrysocycnis, Cyrtidiorchis, Trigonidium). ITS data for 123 species show that all of the segregate genera are embedded within a broad Maxillaria; these segregates usually represent unusual pollination syndromes (e.g., pseudocopulation, moth pollination) or atypical vegetative habits (e.g., Cryptocentrum, Pityphyllum) diverging from the generalized Maxillaria morphology. More intensive sampling across Maxillaria and additional data sets are need before deciding whether or how to divide Maxillaria into smaller monophyletic genera.

Key words: ITS, Maxillariinae, Orchidaceae, trnL-F, Zygopetalinae