A taxonomic study of epiphytic Cactaceae in Rio Grande do Sul State, Brazil, was carried out. The survey presents identification keys, illustrations, ecological and taxonomical observations, geographic distribution, and flowering and fruiting periods of the species. A total of six genera and 13 species were found, two being common accidental epiphytes, Cereus alacriportanus Pfeiff. and Opuntia monacantha Haw., and 11 true or selective epiphytes, Epiphyllum phyllanthus (L.) Haw., Hatiora rosea (Lagerh.) Barthlott, Lepismium cruciforme (Vell.) Miq., L. houlletianum (Lem.) Barthlott, L. lumbricoides (Lem.) Barthlott, L. warmingianum (K. Schum.) Barthlott, Rhipsalis campos-portoana Loefgr., R. cereuscula Haw., R. floccosa Salm-Dyck ex Pfeiff., R. paradoxa (Salm-Dyck ex Pfeiff.) Salm-Dyck and R. teres (Vell.) Steud. One species, R. campos-portoana, is referred for the first time for Rio Grande do Sul State.
Cactaceae; epiphytism; taxonomy; Rio Grande do Sul; Brazil
