The premise that there are genes that wield a strong influence on longevity has, until recently, not been a popular one and there has been no concerted effort to find such genes. However, the finding that single genes can have large effects on the lifespans of yeast, worms and flies raises the possibility that individual genes in mammals may similarly have relatively large effects on longevity. Recent advances in mammalian genetics, many associated with the large-scale efforts to sequence the human and mouse genomes, have accelerated the search for longevity genes, principally in mice. Here, we review results using animal models that have recently shed light on genes regulating longevity and ageing patterns. A large number of genetically defined strains of mice are available and this, together with their established history of use in genetic research and their relatively short lifespans, has made murine models particularly useful. We also review our own work in which genes regulating mouse lifespan and those regulating cell cycling of haematopoietic progenitor cells have been mapped to the same locations in the genome. These results suggest that some of the same genes affect both traits, and further suggest a cause-and-effect relationship between cumulative cell-cycle activity and longevity of an organism.