The graduation thesis is studying upper timberline on the south-western slope of Lastovec in the Savinja Alps. The structure, development and regeneration of tree species in a natural beech forests and a secondary forest of larch andNorway spruce were investigated in this stands. Only small changes in the structure of the beech stands betwen the two measurements were found. In this stands is prevailing species beech, in the upper layers of the stands we foundsmall amount of larch. Replacements forests of larch and Norway spruce are the younger succession stage. Succesion is developing in favour of the dominance of Norway spruce over larch and subsequently in favour of the returnof broadleaves species. But this forests are relative long lasting and stabile succesion phase, that replaced climax community on sites that were forcenturies exploited by humans. We discovered higher density of seedlings inbeech forests (2875/ha). The beech has the highest share in total number of all seedlings in beech forests, following by maple and larch. In replacements forestst is number of sedlings small (325/ha). In seedlings we found three tree species: larch, Norway spruce and mountain ash. The results shows that the actual timber line below Lastovec has been lowered by several hundred metres, however slowly but persistently lifts on more highly altitude.