Antisense oligonucleotides, ribozymes and DNAzymes have emerged as novel, highly selective inhibitors or modulators of gene expression. Indeed, their use in the treatment of diseases arising from genetic abnormalities has become a real possibility over the past few years. The first antisense drug molecule is now available for clinical use in Europe and USA. However, their successful application in the clinic will require improvements in cellular targeting and intracellular delivery. This review aims to look at recent advances in the in vitro and in vivo delivery of antisense oligodeoxynucleotides and ribozymes.