Using nucleotide-specific agents Hoechst 33258, actinomycin D, chromomycin A₃, and distamycin A, the Paris quadrifolia L. karyotype and the location and nucleotide composition of heterochromatic bands were studied. The chromosome idiogram of H33258/AMD and CMA/DA heterochromatic bands was created by an image analysis system with the Videotest-Karyo software. By fluorescence in situ hybridization, the 18S and 26S rRNA genes were mapped.