Neonatal exposure to estrogenic and androgenic endocrine disruptors induces developmental abnormalities in the female reproductive system. To investigate whether neonatal exposure affects oogenesis in juvenile and pubertal ovary, Sprague-Dawley rat pups were given estrogen or various endocrine disruptors by a single injection on the day of birth at concentrations ranging between 2 mM to 40 mM, and sacrificed on day 21 (juvenile) or 50 (puberty). The ovaries were weighed and examined histologically at each stage. Further, 17β-estradiol synthesis of oogenesis was analyzed using normal-phase high-performance liquid chromatography. Neonatal exposure to 17 β-estradiol, diethylstilbestrol and estrogen receptor inhibitors significantly reduced ovary weights, although estrogen receptor inhibitors were completely restored by 17 β-estradiol synthesis during puberty.