Life span is determined by both environmental and genetic influences. The importance of genes is illustrated by the fact that single gene mutations extend life span in nematodes, fruit flies and mice. Recent reports reveal that the life span of Caenorhabditis elegans is controlled by insulin-like signals from the nervous system. Hormones that control life span have recently been identified in fruit flies and mice. These findings suggest that neuroendocrine pathways could constitute an important determinant of life span across phylogeny. This review examines the evidence for nervous system control of longevity and discusses the implications for popular models for aging.