Background. In insects and in mammals, male sperm and seminal fluid provide signaling factors that influence various aspects of female physiology and behavior to promote reproductive success and to compete with other males. It is less apparent how important such signaling is in the context of a self-fertile hermaphrodite species. We have addressed this question in the nematode Caenorhabditis elegans, which can reproduce either by hermaphrodite self-fertilization or by male-hermaphrodite mating. Results. We have studied the egg-laying defective mutant, egl-32, and found that the cellular basis of the egl-32 egg-laying phenotype is likely a defect in sperm. First, the time of egl-32 action coincides with the timing of spermatogenesis in the hermaphrodite. Second, egl-32 interacts with genes expressed in sperm. Third, mating experiments have revealed that wild-type sperm can rescue the egg-laying defect of egl-32 mutant animals. Most importantly, introduction of mutant egl-32 sperm into wild-type hermaphrodites or females is sufficient to induce an egg-laying defective phenotype. Conclusion. Previous work has revealed that C. elegans sperm release factors that stimulate oocyte maturation and ovulation. Here we describe evidence that sperm also promote egg laying, the release of embryos from the uterus.