Abstract: A method for detecting or quantitating multiple copies of a repeat sequence in a nucleic acid molecule involving treating the nucleic acid molecule with a probe which is a nucleic acid analogue which is capable of hybridizing to the repeat sequence in the nucleic acid molecule and which is labelled with a detectable substance. The nucleic acid molecule is treated with the probe under conditions permitting the probe to hybridize to the repeat sequences in the nucleic acid molecule. Probe hybridized to complementary repeat sequences is identified in the nucleic acid molecule by directly or indirectly detecting the detectable substance. The method is preferably used for quantitating multiple copies of a repeat sequence in a nucleic acid molecule, preferably a telomere or centromere repeat sequence. Novel probes for use in the method of the invention and kits are described.