RNA interference mediated by short interfering RNA (siRNA) molecules represents a powerful genetic tool with an increasing interest as potential therapeutics. Current bioinformatic approaches to design functional siRNA molecules take into account both empirical and rational approaches to identify selectable characteristics of active and specific siRNA molecules and focusing the downstream events in the RNAi pathway, such as target messenger RNA accessibility . The design of effective siRNA molecules is the key to successful experimentation with RNAi. Here, we show advanced siRNA design parameters and options for highly efficient siRNA candidate search.