Seven entities ofHieraciumsubg.Hieraciumgrowing in the volcanic area of Mt Amiata were investigated from a karyological viewpoint. Three ploidy levels were found, all with 9 as base number:H. racemosumandH. virgaurea, which belong to the sect.ItalicaFries have 2n= 18 chromosomes with a variable number of terminal satellites;H. sabaudum, H. umbellatum, H. murorumandH. grovesianumhave 2n= 27 chromosomes and probably are agamospermic entities maintaining their morphological identity thanks to the absence of gene-exchange (H. sabaudum-H. umbellatum) or maybe ecological differentiation (H. murorum-H. grovesianum); finallyH. neuropicola, a representative of theH. pallidumgroup that colonizes the trachytic rocks on the top of the mountain, is characterized by a tetraploid set of 36 chromosomes. The finding of diploid populations appears worth evidencing because it provides confirmatory data to the hypothesis of the existence of diploid, maybe sexual and amphimictic cytotypes in Southern Europe. The presence of tri- and tetravalents in respectively triploid and tetraploid entities suggests their autoploid origin.