C. elegans responds to and discriminates among a large number of volatile and water-soluble chemicals using a few defined chemosensory neurons. The functions of individual sensory neurons have been defined by cell killing experiments, and genes required for responses to subsets of chemicals have been identified. C. elegans has several large families of putative chemosensory receptor genes, and one of these genes has been demonstrated to encode a receptor for a specific odorant. Current work is aimed at identifying additional components of chemosensory neuron development and function.