The specific down-regulation of gene expression in cells is a powerful method for elucidating a gene's function. A common method for suppressing gene expression is the elimination of mRNA by RNAi or antisense. Alternatively, oligonucleotide-derived aptamers have been used as protein-directed agents for the specific knock-down of both intracellular and extracellular protein activity. Protein-directed methods offer the advantage of more closely mimicking small molecule therapeutics' mechanism of activity. Furthermore, protein-directed methods may synergize with RNA-directed methods since the two methods attack gene expression at different levels. Here we have knocked down a well-characterized intracellular protein's activity, NFkappaB, by expressing either aptamers or small interfering RNAs (siRNAs). Both methods can diminish NFkappaB's activity to similar levels (from 29 to 64%). Interestingly, expression of both aptamers and siRNAs simultaneously, suppressed NFkappaB activity better than either method alone (up to 90%). These results demonstrate that the expression of intracellular aptamers is a viable alternative to siRNA knock-down. Furthermore, for the first time, we show that the use of aptamers and siRNA together can be the most effective way to achieve maximal knock-down of protein activity.