We have used cationic oligopeptide polyarginine12mer (POA) to deliver double-stranded RNA (dsRNA), prepared in vitro, to tobacco (Nicotiana tabacum) suspension cells. POA interacts electrostatically with dsRNA to form a complex. When dsRNA for the GUS or NPTII gene was delivered into cells carrying the same genes, the corresponding mRNA was degraded. Using RNase protection assay we were able to detect 21-bp small interfering RNA in dsRNA/POAtreated cells. These results demonstrate that POA can be used to deliver dsRNA to induce post-transcriptional gene silencing in plant cells.