The reproductive experiences of pregnancy, parturition and lactation affect a range of neural and endocrine processes following the end of lactation. In women prior parity results in reduced circulating prolactin (PRL) and androgens levels years after giving birth. Reductions in PRL secretion also occur in reproductively experienced, female rats. In the present study we examined the status and regulation of estradiol (E₂) and PRL during the reproductive cycle following reproductive experience. These hormones regulate one another and have been implicated in a number of disease and aging processes. Using a rat model, the patterns of E₂ and PRL secretion, pituitary PRL content, and ER expression were characterized from 1200 to 1800 h on proestrus in age-matched, primiparous and nulliparous animals. The possible effect of parity on estrogen sensitivity was then examined by challenging non-lactating, ovariectomized, age-matched multiparous and nulliparous rats with estradiol benzoate (EB; 0, 1, 5, 25, 125 µg/kg) and measuring PRL responses 24 and 48 h later. Results-prior parity resulted in modest, yet significant, reductions in E₂ and PRL levels on proestrus, a limited increase in pituitary ER expression, and a significant shift in estrogen sensitivity as measured by EB-induced PRL secretion. Nulliparous animals were more sensitive than multiparous rats to the two lower doses of EB, whereas multiparous animals were more responsive to the highest EB dose. These unique parity-induced alterations in the female's endocrine state that persist beyond lactation may impact a multitude of estrogen-mediated processes over the females' adult lifespan.