Abstract: The present invention relates to a method of detecting variant nucleic acid whose nucleotide sequence differs from one another at a single (or more) position(s). The method uses a set of chimeric oligonucleotides containing DNA monomers and monomers of a novel class of DNA analogues, locked nucleic acid (LNA). LNA oligomers obey the Watson-Crick base-pairing rules and form duplexes that are significantly more stable than similar duplexes formed by DNA. The “allele-specific” LNA-containing oligonucleotides wherein the LNA nucleotide(s) are found at the 3′ position can be extended by means of enzymes only where the nucleotide(s), which is/are terminal in direction of extension, is/are complementary to the corresponding nucleotides of the nucleic acid (of the one allele) to be detected. Thus discrimination between alleles without subsequent differential hybridization with labelled oligonucleotides is possible.