One of the major recent discoveries in molecular and cellular biology is that small double-stranded RNA molecules selectively turn off gene expression in all types of cell, a phenomenon known as RNA silencing. This discovery led to the development of RNA interference (known as RNAi) as a powerful research tool in the functional study of individual genes and their products, and in functional genomics. In RNAi, specific small double-stranded RNA molecules (small interfering RNAs or siRNAs) are introduced into cells to selectively silence certain genes.RNAi covers the basic concepts and mechanisms of RNAi, transfection of cells with siRNAs, the design and validation of RNAi reagents, RNAi techniques in different organisms, large-scale RNAi screening, applications of RNAi in drug discovery, and potential uses of RNAi as a therapeutic agent. A key feature of RNAi is the highlighting of the pitfalls that can occur and how to minimize them. The book also contains a complete list of abbreviations.