In principle, RNA interference (RNAi) is a straightforward method for inducing sequence-specific silencing of one or more genes of interest with the simple introduction of small interfering RNAs (siRNAs). In practice, there are fundamental challenges to be considered in order to achieve successful gene silencing. Among these are siRNA design and production, as it is well known that not all siRNAs directed against a given target silence with equivalent efficiencies. Thus, identification of sequence related elements that are critical for functionality are important in the development of this new and potent technology. Similarly, there is a variety of methods available for producing the small functional duplex intermediates, the choice of which is largely driven by time, labor, and cost considerations.