Aging is a universal but poorly understood biological process that involves a complex interplay between environmental and genetic factors. Model organisms such as C. elegans and Drosophila have provided an opportunity to search for and identify specific genes that affect life span. Interestingly, increasing evidence suggests that many of these genes affect lifespan by exerting their effects in a limited number of cell types and, in particular, neurons, indicating that the nervous system may be a central regulator of organismal lifespan.