Koehler, S. and Amaral, M.C.E. (Depto. Botânica, Universidade Estadual de Campinas, C.P. 6109, Campinas, SP, 13083–970, Brazil; skoehler@unicamp.br). A taxonomic study of the South American genus Bifrenaria Lindl. (Orchidaceae). Brittonia 56: 314–345. 2004.—A taxonomic study is presented for the South American orchid genus Bifrenaria Lindl., which is characterized, within the subtribe Maxillariinae, by four-angled, unifoliate pseudobulbs, plicate leaves, and by flowers bearing a conspicuous spur and a pollinarium usually with a forked stipe. We consider Bifrenaria a monophyletic group including Adipe (=Stenocoryne), Cydoniorchis, and Bifrenaria sensu stricto. The main goals of this study are to present a taxonomic synopsis of genus Bifrenaria, determining which taxa should be recognized, their distributions, and which characters traditionally used to discriminate species are taxonomically informative. Identification keys, descriptions, distribution maps, and line drawings are also provided.