Numerous theories of ageing have been proposed, and many have been tested experimentally, particularly using nematode models such as Caenorhabditis elegans. By combining those theories of ageing that remain plausible with recent findings from studies of C. elegans life span mutants, an integrated theory of ageing has been devised. This is formed from 3 interconnected elements: the evolutionary theory of ageing, the oxidative damage theory of ageing, and a nonadaptive programmed ageing theory. This tripartite theory of ageing gives rise to a number of predictions that may be tested experimentally.