We separated immunoglobulin from goatsera by Kekwick method and incubated with radioactive estradiol labeled estradiol receptor (ER). We investigated whether immunoglobulin formed a complex with ER or not with sucros gradient cnetrifugation. WE investigated how often type II IgG (IgG wich bind estradiol receptor nonspecific) exists in differents species. Keywords : nonspesific binding, estrodiol receptor, immunoglobulin