A process for detecting a presence of steroid receptors in tissue therapeutically and for treating certian tissue, especially tissue having estrogen receptors, includes the step of treating the tissue by injection, surface application or the like, with a labeled steroid. The labeled steroid may include a moiety which is readily imageable on a gamma radiation detector, on x-ray film, on a fluoroscope, through NMR devices or the like. An especially suitable labeled steroid has been found to be 16-.sup.123 I-17-beta-estradiol having a specific activity of greater than 2,000 curies per millimole and preferably at least 5,000 curies per millimole.