In house crickets [Acheta domesticus (L.)] a single mating early in adult life sufficed to induce egg laying for the duration of the life of a female. Female house crickets mated readily shortly after adult emergence but oviposition did not commence until about 12-14 days after emergence, even though females matured eggs by 7 days. The egg-laying factor associated with mating remained active during prolonged periods of substrate deprivation during which the female did not oviposit. If the spermatophore was removed prematurely shortly after a mating, the long-term, egg-laying response was truncated and was correlated with a dramatic decline in the fertility of eggs which were oviposited. The egg-laying stimulus appeared to act in the spermatheca, apparently through neural means, since denervation of the spermatheca abolished mating-induced oviposition. These results indicate that the oviposition factor found in the testes is able to act for long periods of time and has to be present continually in order to be effective. Furthermore, the long-term oviposition stimulus in the house cricket may be different from prostaglandin E2 which induces a prompt ovipositional response.