This study presents a list of species of the two most important families with epiphytic elements, Bromeliaceae and Orchidaceae, from the Reserva de la Biosfera Barranca de Metztitlán (RBBM), the largest Reserve in Hidalgo, Mexico. Thirty-four species are included, 26 corresponding to species in three genera of bromeliads, and eight species in six genera of orchids. The new records represent 26.5% of the total listed in the area; nine of them are new records for the Reserve (RBBM) and one is new for Hidalgo State. This study reveals that endemism for both families is very important in the Reserve (55.88%), since it includes 13 Mexican bromeliads, of which two are endemic to Hidalgo and one to the Reserve, and three orchids, two endemic to Mexico and one to the Reserve. We found species with different types of relative abundance: rare (16) and occasional (7). Additionally, we include information about the category (IUCN, CITES, NOM-059-SEMARNAT) as well as uses reported in the literature for the species in the RBBM. The checklist is strictly based on information obtained from deposited herbarium specimens as well as from those collected during fieldwork. We suggest that a conservation plan (in situ and ex situ) for the RBBM is important and necessary. The predominant habit for both families is epiphytic (17 species); even though there are terrestrial (7) and saxicolous (2), and the remaining are facultative species (8). Nine species are included in some risk category. The present work is the most complete and updated list of Bromeliaceae and Orchidaceae for this important natural area in the Mexican State of Hidalgo. However, more fieldwork is needed to document the biodiversity of the area in general and its flora in particular, as a way to highlight the importance of protected areas in preserving biodiversity.
