As in previous years, modified oligonucleotides continue to attract much research. The scope for modifying oligonucleotides is quite broad, nucleobase, sugar or the internucleotide linkage, and a combination of each. This review covers literature for 2011 ealing with modified oligonucleotides, though unlike previous years the sections on aptamers and ribozymes, and nucleic structures are excluded, but will be dealt with in the next volume.