Oligo(2'-O-alkylribonucleotides) have been developed recently as novel oligonucleotide analogues with properties that enhance their use as antisense probes. They possess high chemical stability and are resistant to hydrolysis by DNA- or RNA-specific nucleases. Many forms of oligo(2'-O-alkylribonucleotides) hybridise specifically and efficiently to complementary RNA sequences, forming stable duplexes that are not substrates for cleavage by RNAse H. In combination with prosthetic reporter groups, such as biotin, DNP or fluorophores, oligo(2'-O-alkylribonucleotides) have important applications in a wide range of biochemical studies on RNA function and structure.