Introduction. In the early 1990s, during experiments aimed at intensifying the colour of Petunia hybryda flowers, a new mechanism of regulation of gene expression was discovered; however, its mechanism, i.e. inhibition of gene expression at a post-transcriptional stage, remained unknown. In 1998 two groups led by A. Fire and C. Mello found a molecular basis for the phenomenon called RNA interference (RNAi). Delivery of a double stranded RNA to a model organism, Caenorhabditis elegans, triggered silencing of complementary messenger RNA sequences. This discovery opened new perspectives for research involving gene functions due to the possibility of inhibiting the expression of a specific gene through its mRNA degradation in the cytosol. Aim. The aim of this paper is to present a potential role of RNAi as a therapeutic method for various diseases. Discussion. RNAi provides a powerful technique for the derivation and analysis of loss-of-function phenotypes in vertebrate cells. This technique may be also applied as a therapeutic strategy, e.g. in genetic and viral diseases, and clinical trials to test this possibility have been already initiated. Conclusions. RNAi-based therapy may become a powerful tool to treat many diseases whose molecular pathogenesis mechanisms have been thoroughly understood.