The floristic composition and phytosociological structure of the "Morro Osório", in the municipality of Osório, located on the coast of the State of Rio Grande do Sul, were studied from data collected in a forest inventory carried out in 10 sample units with dimensions of 10 x 100m (1000m 2 ), where all individuals with CAP> = 45cm were identified and raised. In each one of them were distributed two cencentric circular subsamples, one of 10m 2 (radius = 1,78m) and one of 100m 2 (radius = 5.64m 2 ), for the analysis of the individuals in natural regeneration in the classes from 0 to 15 and 15 to 45cm of CAP, respectively. It was identified 65 species, belonging to 58 genera of 30 botanical families. Allophylus edulis(St. Hil.) Radlk., Cabralea canjerana (vell.) Mart. Cupania Vernalis Camb., Falcata Erythryna Benth., Inga marginata Willd. Divaricata Luehea Mart. Nectandra megapotamica (Spreng.) Nees., Pachystroma longifolium ( nees.) IM Johnston., Trema micranta (l.) Blume. and Trichilia claussenii C. DC. are among the most characteristic and important species of the association.
