Leaf anatomical characterization of Guzmania Ruiz & Pav. and Mezobromelia L.B.Sm. (Tillandsioideae, Bromeliaceae)). Guzmania and Mezobromelia (sensu Smith & Downs 1979) are paraphyletic genera, and the recent transfer of species between them demonstrates an unstable systematics. By using leaf anatomical characters, we expect to contribute to the discussion of generic boundaries and to search for possible morphological adaptations in the leaves of species distributed in different environments. We sampled leaves of eight species of Guzmania and one of Mezobromelia collected across South America and described them under light and scanning electronic microscopy. Also, we compared our results with previous descriptions. Trichome morphology, particularly the shape of shield cells, number of cells, as well as the shape of the air channels in the mesophyll proved to be informative to segregate species of Guzmania, reinforcing leaf anatomy as a tool to taxonomy. We could segregate Mezobromelia from Guzmania species based on variation of fiber distribution in the mesophyll, presence of silica bodies in epidermal cells and arrangement of trichomes. This corroborated placement of these genera in distinct tribes. No strong selection in response to habitat was found with the data collected here. We suggest that further sampling and more anatomical investigation will help to elucidate relationships in the Mezobromelia-Cipuropsis complex, as recently defined. Key words: Cipuropsis, epiphyte, leaf anatomy, morphology, Tillandsieae, trichomes, Vrieseeae