Sex-related differences in longevity are common throughout the animal kingdom. Previous studies have suggested that at least part of these differences may be due to sex-specific costs of reproduction. Recently, workers have recognized that sexual conflicts of interest between males and females may play a significant role in the evolution of sexually dimorphic traits. Here I explore the possibility that sexual conflict may explain sex-specific differences in longevity and may act as a driving force in the evolution of senescence. I present comparative evidence for this hypothesis and discuss the potential relevance of sexual conflict theory to the search for specific genes that influence longevity. One implication of a sexual conflict theory of aging is that genes that influence senescence, and in particular those that affect sex differences in aging, may evolve very rapidly and so be difficult to detect.