The effect of 2-hydroxyestrone, 2-hydroxyestradiol and estriol on binding to cytosol receptors of dimethylbenzanthracene-induced rat mammary tumors was investigated. All three steroids bind to a high affinity estrogen receptor with 2-hydroxyestradiol having twice the affinity for tumor cytosol receptors than estriol or 2-hydroxyestrone. Both 2-hydroxyestradiol and estriol were able to translocate tumor cytosol receptor to the nucleus. Furthermore, experiments on the in vivo effect of these steroids on the nuclear accumulation and retention of estrogen receptors by rat uterus showed that 2-hydroxyestradiol and estriol caused significant nuclear receptor translocation with short retention time which is paralleled by a corresponding short term uterine growth responses. However, 2-hydroxyestrone was unable to induce receptor translocation or uterine growth effects.