o,p'-DDE is a metabolite and degradation product of the organochlorine pesticide DDT. It accumulates in smallmouth buffalo, channel catfish, and largemouth bass as well as sediment in the Huntsville Spring Branch-Indian Creek tributary system surrounding a DDT manufacturing plant where it is considered a persistent organic pollutant (POP). o,p'-DDE inhibits estrogen binding to rainbow trout estrogen receptors (rtERs) with an IC50 value of 3.2 μM. It induces concentration-dependent secretion of estradiol by granulosa and theca cell co-cultures isolated from porcine ovarian follicles. In ovo exposure to o,p'-DDE increases degeneration of ovarian follicles and reduces testicular size in Japanese medaka (O. latipes).