Concentrations of 25, 50 or 100 ppm of 95% purified zearalenone fed to healthy, multiparous sows during pre-estrus or throughout the gestation period (or both) produced multiple reproductive deficiencies. These reproductive disorders included infertility, constant estrus, pseudopregnancy, diminished fertility, reduced litter size, smaller offspring, malformation, juvenile hyperestrogenism and probably fetal resorption. Gross and histologic examinations of sows revealed various lesions in the reproductive organs. Marked epithelial changes characterized by squamous metaplasia were noticed in the uterus, uterine duct, cervix, vagina and mammary glands.