Hieracium transylvanicum is a relic species which occurs in refugial areas of south-eastern Europe. The structure of its karyotype, including determination of morphometric features of somatic metaphase chromosomes as well as the number and distribution of ribosomal DNA loci, was attempted using both classical chromosome staining and the FISH method with 25S rDNA and 5S rDNA probes. The cytotypes under study were collected from eight sites and did not vary significantly in terms of their karyotype organisation. All 11 specimens had the same chromosome number, 2n=2x=18, and 9 similar chromosomal types, whose total length ranged from 4.62 to 2.64 μm. The karyotype of the species is highly symmetrical. Two chromosomal types, 3 and 6, have a 45S rDNA locus in distal parts of their short arms. In addition, the short arm of type 6 has interstitial 5S rDNA sequences. No intraspecific variation in number and chromosomal distribution of ribosomal DNA loci was observed. The very uniform structure of the karyotype of H. transylvanicum possibly refl ects the old phylogenetic age of this species.