In Drosophila females, mating is known to cause a reduction in life span, which is referred to as 'the cost of mating'. Since mating enhances oogenesis and oviposition, the cost of mating may be regarded as a trade-off between reproduction and longevity. We examined whether the cost of mating exists in mutant females that are unable to produce eggs. Three different mutant alleles of ovarian tumors (otu) and an allele of dunce (dnc(M11)) of Drosophila melanogaster were used to sterilize females. For all the female sterile mutants tested, mating dramatically decreased the life span of homozygous sterile females. Even more extreme shortening of life spans were observed when the sex peptide gene (Acp70A) was expressed in homozygous otu females, though they were virgin, indicating that the shortening in life span is due to seminal factors. These results indicate that the cost of mating is greater in females defective in oogenesis than that in normally fertile females.