4'-C-Hydroxymethylthymidine was converted to 4'-C-methoxymethylthymidine and 4'-C-aminomethylthymidine, which were incorporated into oligodeoxynucleotides by phosphoramidite chemistry. The modified oligonucleotides exhibit excellent hybridization and significant improvement in stability to snake venom phosphodiesterase. Copyright (C) 1996 Elsevier Science Ltd