In the course of preparing generic treatments of Pleurothallidinae of Brazil, material of several genera was examined and their morphologies and nomenclature elucidated. One species is described as new and sixteen are proposed as synonyms. Illustrations, updated synonym lists, typifications, and taxonomic discussions are provided. Genera and species follow in alphabetical order.Abstract. 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. . We thank the folowing herbaria for the privilege of visiting their collections and permission to reproduce images of herbarium specimens: AMES, BM, BR, C, HB, K, LE, P, MO, MBML, NY, RB, SEL, SP, UPCB, and W. We are also grateful to Ronaldo Herculano Alves, Maria Rita Cabral, and Maria do Rosário de Almeida Braga for providing material of Acianthera agathophylla for study; Luiz Filipe Varella for permission to reproduce some of his photographs and for providing material for study; Leslie Garay for helping to interpret Reichenbach's collections and handwriting, and also for sending literature; Thiago Meneguzzo for assistance in locating literature and specimens at RB; Rudolf Jenny for sending literature; Eric Smidt for sending images and for helping prepare specimens for UPCB; Nancy Karam and Wade Collier for help in assembling the illustrations; Stig Dasltröm for inking the illustrations, and the Pleurothallidinae Alliance for making it possible.