A floristic and phytosociological survey of the tree commnunity was carried out in a fragment of sub-montane semideciduous forest located on the margin of the Dona Rita Hydroelectric Reservoir, municipality of Itambé do Mato Dentro, State of Minas Gerais, south-eastem Brazil (19°26‘S, 43°14‘W, 610-630m of altitude). All individuais with a stem diameter at the base, of dbt ≥5cm (lianas excepted) found in thirty five 15×15m quadrats, Were identified, measured (dbt) and had their height estimated (individuais found outside quadrats with reproductive structure were also collected). The following phytosociological parameters were calculated for all species: density per area, absolute frequency, absolute dominance calculated from the basal area, and importance value. The Shannon diversity index and the corresponding evenness were calculated. Jaccard’s similarity indices and euc1idian distances were also calculated among the studied forest and other forests surveyed in the following regions of Minas Gerais State: Upper and Mid Rio Grande, Lower Rio Paranaíba and Upper Rio São Francisco. A total of 2,430 individuais were recorded in the sample area. These belonged to 50 families, 144 genera and 216 species. The following families produced the highest importance values: Euphorbiaceae, Myrtaceae and Caesalpiniaceae. The most important species were Apuleia leiocarpa, Pera glabrata, Licania hypoleuca, and Mabea fistulifera. A comparison with the other areas indicated that the forest of Itambé do Mato Dentro is more similar to those of the Upper Rio Grande which are all under a stronger floristic influence of the Atlantic Forest, although the most important species are not the same. The soils of the area are deeper, highly weathered and leached, despite the strongly sloping topography because they had gone through an intense process of alteration prior to the present pedogenetic cycle.