Using a systemic and continuous delivery method based on feeding on a particular strain of transformed Escherichia coli to induce double stranded RNA-mediated interference, we targeted the product of the npr-1 gene, a putative Caenorhabditis elegans homologue of a neuropeptide Y receptor, a G-protein coupled receptor. We were able to reproduce the social behaviour observed for the naturally occurring npr-1 mutant when wild type N2 Bristol eggs developed in a lawn of bacteria producing double stranded RNA for npr-1. This facile approach may also be useful when studying the function of other worm G-protein coupled receptors.