Estrogen has dramatic effects on the development and function of the reproductive tract in mammals. Although diethylstilbestrol (DES) triggers the development of reproductive organs in immature animals, continued exposure to DES induces dysfunction of the female reproductive tract in mice. To investigate the effects of neonatal estrogen exposure on the reproductive tract of female chickens, we implanted DES pellets into the abdominal region of immature female chicks and then examined the effects of DES on the oviducts of both immature chicks and sexually mature chickens (30 weeks old). DES induced mass growth and differentiation of the oviduct in immature chicks. The chick oviduct increased by 2.7- and 29-fold in length and weight, respectively, following primary DES stimulation. In secondary DES stimulation, the length and weight of the chick oviduct increased by 4.5- and 74-fold, respectively. Additionally, DES treatments caused abnormal development of the infundibulum and magnum in hen oviducts. Furthermore, infundibulum abnormality gave rise to unusual ovulation of follicles and resulted in infertility and dysfunction of the magnum, such as less production of egg white proteins. Our results indicate that DES exposure during early developmental stages in chickens has detrimental effects on the development and maintenance of the female reproductive tract after sexual maturation.