An estrogen binding protein for estradiol-17beta is present in the liver cytosol of female intact and one day oophorectomized rats. The dissociation constant reveals high affinity binding (Kd: 0.69 +/- 0.14 times 10(-10) M). Quantitation of EBP using a dextran-coated charcoal method shows that this specific macromolecular binding is much less than in the rat uterus, but similar to that in DMBA-induced mammary tumors. Sucrose density gradient analysis shows sedimentation at 8-9 S and 4-5 S when compared to bovine serum albumin.