Abstract: A method aimed at the quantification of di- and trinucleotide repeat which includes (a) treating a sample containing the nucleic acids of interest to obtain unpaired nucleotide bases spanning the position of the repeats and flanking regions, if the nucleic acids are not already single stranded; (b) contacting the unpaired nucleotide bases with an oligonucleotide primer capable of hybridizing with a stretch of nucleotide bases present in the nucleic acid of interest preferably 3' of the trinucleotide repeats to be quantified, so as to form a duplex between the primer and the nucleic acid of interest; (c) providing means to ensure that the examined nucleic acid and the oligonucleotide primer are confined to a reaction chamber at all further steps; (d) contacting the duplex with a primer extension unit which is capable of base pairing with the first nucleotide base in the core sequence of the repeats, and a template dependent extension enzyme; (e) eliminating non-incorporated primer extension units; (f) contacti