2′-O,4′-C-methylene-linked ribonucleotide derivatives, named LNA (locked nucleic acid) and BNA (bridged nucleic acid) are nucleic acid analogoues that have shown high-affinity recognition of DNA and RNA, and the employment of LNA oligomers for antisense activity, gene regulation and nucleic acid diagnostics seems promising. Here we show kinetic and thermodynamic results on the interaction of a series of 10 bases long LNA–DNA mixmers, gabmers as well as full length LNA's with the complementary DNA, RNA and LNA oligonucleotides in the presence and absence of 10 mM Mg²⁺- ions. Our results show no significant differences in the reaction thermodynamics and kinetics between the LNA species, only a tendency to stronger duplex formation with the gabmer and mixmer. Introduction of a few LNA's thus may be a better strategy, than using full length LNA's to obtain an oligonucleotide that markedly increases the strength of duplexes formed with the complementary DNA and RNA.