SUMMARY Total nuclear uptake of oestradiol, specific nuclear binding of oestradiol and oestrogeninduced proteins were studied in the uterus of female Sprague–Dawley rats injected on postnatal day 3 with sesame oil or with 1·25 mg of testosterone propionate in sesame oil (androgenization). Total uptake of radioactivity was lower than normal in nuclei from uterine homogenates of androgenized females but was increased by the addition of excess cytosol from normal uterus. These data suggest that androgenization increases the uterine cytosol proteins which inhibit translocation of oestradiol to the cell nucleus. Androgenization also reduced specific (5 S) nuclear binding of oestradiol and the formation of oestrogeninduced proteins.