Recent years have seen a rapid increase in studies of nanoparticle toxicity. These are intended both to reduce the chances of unexpected toxicity to humans or ecosystems, and to inform a predictive framework that would improve the ability to design nanoparticles that are less likely to cause toxicity. Nanotoxicology research has been carried out using a wide range of model systems, including microbes, cells in culture, invertebrates, vertebrates, plants and complex assemblages of species in microcosms and mesocosms. These systems offer different strengths and have also resulted in somewhat different conclusions regarding nanoparticle bioavailability and toxicity. We review the advantages offered by the model organism Caenorhabditis elegans, summarise what has been learned about uptake, distribution and effects of nanoparticles in this organism and compare and contrast these results with those obtained in other organisms, such as daphnids, earthworms, fish and mammalian models.