C. elegans is sensitive to the majority of anthelmintic drugs that are used against parasitic worm infections of humans and livestock. This has provided the opportunity to use molecular genetic techniques in the worm for mode of action studies. These approaches continue to be of considerable value to the field of parasitology. In addition, there are numerous examples of anthelmintic drugs providing exceptionally useful pharmacological tools to delineate fundamental aspects of cell signalling in C. elegans. This has primarily been achieved through the use of anthelmintics in forward genetic screens followed by the mapping and characterization of genes that confer altered susceptibility to the drug. Less fruitful so far, but nonetheless useful, has been the direct use of C. elegans for anthelmintic discovery programmes. In this brief review we provide an introduction to the use of C. elegans as a 'model parasite', outline the actions of the main classes of anthelmintics, and highlight approaches that have been of particular value.