Theories of life-history evolution propose that trade-offs occur between fitness components, including longevity and maximal reproduction. In Drosophila, female lifespan is shortened by increased egg production, receipt of male accessory fluid and courting. Male lifespan is also reduced by courting and/or mating. Here we show that in the nematode Caenorhabditis elegans, mating with males reduces the lifespan of hermaphrodites by a mechanism independent of egg production or receipt of sperm. Conversely, males appear unaffected by mating. Thus, in C. elegans there is no apparent trade-off between longevity and increased egg or sperm production, but there is a substantial cost to hermaphrodites associated with copulation.