The 2006 Nobel Prize in Physiology or Medicine was awarded to Andrew Z. Fire and Craig C. Mello for their discovery of RNA interference (RNAi). RNAi is a biological process in which RNA molecules can silence (inhibit) or up- or down-regulate gene expression, typically by causing the destruction of specific messenger RNA (mRNA) molecules. This collection of articles begins with an introduction to RNAi, and proceeds to describe uses of this technology in various approaches to disease treatment, including gene therapy. Several laboratory protocols for silencing genes via RNAi are also provided, as are protocols for down-regulating and then rescuing those down-regulated genes, which demonstrates specificity of the approach. This e-book — a curated collection from eLS, WIREs, and Current Protocols — offers a fantastic introduction to the field of RNA interference for students or interdisciplinary collaborators. Table of Contents: Introduction Overview of Gene Silencing by RNA Interference Current Protocols in Nucleic Acid Chemistry Daniel H. Kim, John J. Rossi Biogenesis and function of endogenous and exogenous siRNAs WIREs RNA Nicholas M. Snead, John J. Rossi Techniques & Applications Small Silencing RNAs and Gene Therapy eLS Dirk Grimm RNAi Screening: New Approaches, Understandings, and Organisms WIREs RNA Stephanie E. Mohr, Norbert Perrimon Delivery of RNAi mediators WIREs RNA Lance P. Ford, Masoud M. Toloue Protocols Silencing of Gene Expression in Cultured Cells Using Small Interfering RNAs Current Protocols in Cell Biology Kumi Sakurai, Pritsana Chomchan, John J. Rossi Gene Down-Regulation with Short Hairpin RNAs and Validation of Specificity by Inducible Rescue in Mammalian Cells Current Protocols in Cell Biology Hoi Tang Ma, Randy Y.C. Poon