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Rare species are one of the principal components of the species richness and diversity encountered in Dense Ombrophilous Tropical Forests. This study sought to analyze the rare canopy species within the Atlantic Coastal Forest in Rio de Janeiro State, Brazil. Six diVerent communities were examined: Dense Ombrophilous alluvial Forest; Dense sub-montane Ombrophilous Forest; Dense Montane Ombrophilous in Serra do Marand Serra da Mantiqueira. In each area the vegetation was sampled within forty 10 £ 25 m plots alternately distributed along a linear transect. All trees with DBH (1.3 m above ground level) ¸5 cm were sampled. The canopy was characterized using the allometricre lationship between diameter and height, and included all trees with BDH ¸10 cm and height ¸10 m. A total of 64 families, 206 genera, and 542 species were sampled, of which 297 (54.8%) represented rare species (less than one individual per hectare). The percentage of rare species varied from 34 to 50% in each of the diVerent communities sampled. A majority of these rare trees belonged to the Rosidae, and a smaller proportion to the Dilleniidae. It was concluded that there was no apparent pattern to rarity among families, that rarity was probably derived from a number of processes (such as gap formation), and that agreat majority of the rare species sampled were consistently rare. This indicates that therestricted geo graphic distribution and high degree of endemism of many arboreal taxa justi-Wes the conservation of even small fragments of Atlantic Forest. [ABSTRACT FROM AUTHOR]