A review.As the pharmaceutical industry struggles to develop effective small mol. drugs, attention is beginning to turn to regulating endogenous mRNA levels, rather than inhibiting protein function.Two main methods for achieving this are discussed.Firstly, antisense technol. involves the addition of a short oligonucleotide complementary to the target mRNA, leading to the formation of a double-stranded DNA-RNA hybrid.This either inhibits translation and/or induces RNAse H digestion of the mRNA.Secondly, RNAi within cells is induced upon the addition of dsRNA.This activates a complex pathway whereby the dsRNA is firstly cleaved by the RNase III-like protein Dicer, generating 21-25 nt siRNAs.These are then bound by the RISC complex, which degrades mRNAs homologous to the siRNAs.Both these methods of mRNA suppression have various obstacles to overcome before they can be seriously considered as potential therapeutic agents, most notably those of stability of the agent and delivery to the target tissue(s).Recent advancements in the field are, however, making this possibility look increasingly likely.