RNAi is an effective method for analyzing gene function in C. elegans that often phenocopies loss-of-function phenotypes (1). In RNAi, double stranded RNA (dsRNA) introduced into larvae or adults activates an enzymatic pathway that eliminates endogenous RNAs homologous to the dsRNA (2). Potent and persistent RNAi silencing in results from secondary amplification of small amounts of the initial RNAi trigger by RNA dependent RNA polymerases (3, 4). RNAi can be induced in C. elegans using one of four methods: injecting in vitro synthesized dsRNA into the body cavity of the animal (injection RNAi), soaking in a solution of dsRNA (soaking RNAi), feeding animals bacteria engineered to express dsRNA (feeding RNAi), or through creation of transgenic animals that express dsRNA from DNA arrays maintained within cells (hairpin RNAi) (5, 6). This protocol is slightly modified from (7), and can be used for candidate or broad RNAi screens in C. elegans (8, 9).