Using the (unweighted) average linkage clustering (UPGMA) method we classified 458 phytosociological relevés of Larix decidua forests in the Southeastern Alps into 25 clusters. Based on their analysis we described the following new subassociations: Rhodothamno-Laricetum deciduae geetosum rivalis, sorbetosum chamaemespili, piceetosum abietis, adoxetosum moschatellinae, cystopteridetosum fragilis, cyclaminetosum purpurascentis, dryadetosum octopetalae and sorbetosum ariae. The selected method proved adequate in identifying the differences between larch stands on potential subalpine spruce and beech sites, and larch forests on the upper forest line, as well as the differences between initial larch stages on the upper forest line and more stable development stages on better developed soils on promontories and ledges above the upper beech forest line. Larch forests occur mainly in the altitudinal belt between (1,500) 1,600 and 1,800 (1,900) m, on shady aspects and slopes that are steeper than 30°. They are some of the best preserved forest types in the Southeastern Alps, on smaller surface areas (Macesnje above the Beli Potok valley in the Julian Alps) even virgin forests, and their role as biotopes is exceptional.