In situ hybridization on somatic metaphâse chromosome from sunflower root tips, by detection system of biotin-labeled DNA using streptavidin-alkaline phosphatase conjugate, was performed at INRA-Dijon, France. The metaphase chromosome slides were developed using 1.5 cm root tips of inbred lines CG-8034 and H-13L16, from ICCPT Fundulea, România. After nin sin" hybridization during 24 hours of incubation with biotin-labeled DNA (5 S ribosomal DNA of 330 bp), the microscopical view showed the signals at the end of the chromosomes, associated with satellites. Repetitive DNA sequences detected directly on somatic metaphase chromosomes are localized at the heterochromatic regions in the satellites.