Vitellogenesis, an important reproductive process in oviparous animals, includes the processes of hormonally regulated synthesis of yolk precursor protein, vitellogenin (Vg), and their deposition in ovarian oocytes as a vitellin which is an important energy source as well as buoyancy regulator of the egg. Vg genes consist of a gene family that encompasses a large number of lipoproteins and produce different Mr. Vg proteins in liver. The expression of Vg is largely dependent on the estrogen, and both reproductive cycle and temperature also influence Vg synthesis. Synthetic estrogens or estrogenic pollutants was sufficient to induce Vg in both sexes of oviparous vertebrates. Therefore, the estrogenic induction of vitellogenesis in male has been used for biological marker in the screening of estrogenicity of certain endocrine disrupting compounds and the monitoring the world-wide contamination of estrogenic compounds in wild life. In the studies on the biological hazard and influence of endocrine disrupting chemicals using the Vg induction in oviparous males, it is important to consider the reproductive cycle, zoogeography and biodiversity of the wild life animals in Korea.