Discovery of RNA-mediated interference (RNAi) is widely recognized as one of the most significant molecular biology breakthroughs in the past 10 years. There is a need for science educators to develop teaching tools and laboratory activities that demonstrate the power of this new technology and help students to better understand the RNAi process. "C. elegans" is an ideal model organism for the undergraduate laboratory because of the simplicity of worm maintenance, its well-studied genetic background, and the fact that it can be employed as a model organism in laboratory environments where vertebrate research is restricted. Certain unique features of "C. elegans" make it a very suitable organism for RNAi studies. Specifically, nematode strains highly sensitive to RNAi are readily available from public sources, and RNAi induction by a feeding method is an uncomplicated procedure that lends itself readily as an educational tool. In this article, we provide a detailed depiction of the use of "C. elegans" as an RNAi educational tool, describing two separate RNAi-based experiments. One is a qualitative experiment where students can examine the effects of knocking down the "unc-22" gene involved in the regulation of muscle contraction, which results in a twitching phenotype. The other experiment is a quantitative RNAi experiment, where students measure the effect of knocking down the "lsy-2" gene involved in neuronal development. Although these experiments are designed for a college-level study, nematode research projects can also be accomplished in secondary school facilities. (Contains 5 figures, 6 tables and 1 footnote.)