One new species in the genus Acianthera, A. imitator, is described and illustrated. Sixteen species are proposed as synonyms. They are listed in alphabetical order: Acianthera gradeae as synonym of A. agathophylla; A. spilantha as synonym of A. breviflora; A. antennata as synonym of A. gracilisepala; A. dichroa as synomym of A. strupifolia; Anathallis crebrifolia, A. montipelladensis, and A. ourobranquensis as synonyms of A. aristulata; A. liparanges as a synomym of A. heterophylla; A. bolsanelloi, A. githaginea, and A. nectarifera as synonyms of A. lobiserrata; A. limbata and A. marginata as synonyms of A. muscoidea; A. longiglossa as synonym of A. paranaensis; Lankesteriana gehrtii as synonym of L. caudatipetala, and Specklinia rubidantha as synonym of Lankesteriana imberbis. Correct provenance and habitat information are provided for the type collection of the recently described Anathallis johnsonii. This species is herein formally recorded for Brazil. Lectotypes are selected for seven species: Anathallis heterophylla, A. nectarifera, Lepanthes crebrifolia, Pleurothallis gracilisepala, P. microgemma, P. paranaensis, and P. spilantha, and an epitype is selected for Pleurothallis paranaensis. Illustrations and taxonomic discussions are also provided.