We previously synthesized bridged nucleic acid (BNA) analogues possessing an S-type sugar conformation. Recently, we achieved the synthesis of a 2'-deoxy analogue of trans-3',4'-BNA. The structure of this compound was confirmed by X-ray crystallography, which indicated that its sugar ring had an S-type conformation. The hybridization ability of the 2'-deoxy-trans-3',4'-BNA-modified oligonucleotide with DNA and RNA complements was evaluated, and it was found that 2'-deoxy-trans-3',4'-BNA showed superior hybridization ability compared with other BNA analogues with S-type sugar conformation.