Five rainforest areas situated inthe Itatiaia Mountain Range,states ofMinas GeraisandRio de Janeiro,SEBrazil, were surveyed in order to produce a checklist of tree species of the regional forests. This checklist resulted from floristic surveys carried out in the five forest fragments, and phytosociological surveys in three of them. An additional checklist produced for a forest area situatedon the Itatiaia southern slopes, state of Rio de Janeiro, was extracted fromthe literature to help assessing the variations in floristic composition. The tree flora sampled in the five studied areas was composed of 450 species, 191 genera and 69 families, many of which are known as characteristic ofmontane forests (situated above 1,000m of altitude). The tree flora of the Itatiaia Range forests may be considered as one of the richest in species among areas of montane rain forest in SE Brazil. A cluster analysis identified patterns of floristic similarityamongthe six forest areasof the ItatiaiaRangewhichwere related to the occurrence of periodic floods in an area of alluvial rain forest, to differences in slope aspect (oceanic or continental) among the five areas of montane rain forest, and to the early sucessional stage of one of these. The highest similarity was obtained between the areas of mature montane rain forest of the continental slope, in Aiuruoca and Bocaina de Minas, although the geographical distance between them was much greater than the distances between the latter and the areas of alluvial forest and early sucessional forest.