RNAi-mediated silencing is now being used in multiple species, from plants to humans, to identify gene functions. This new technology is fully exploited in Caenorhabditis elegans, since an RNAi feeding library that has the potential to inactivate 86% of the predicted genes of the C. elegans genome is publicly available. This tool made systematic screening of genes involved in biological processes of interest easier, but there are some pitfalls: specificity, reproducibility and hypomorphic effects. However, as with any other technology, RNAi is getting better as time goes on. Once these caveats are taken into account, RNAi-mediated silencing is still a very powerful approach to identify new gene functions and to dissect complex pathways.