Breast cancer, prostate cancer, endometrial cancer, and lymphocytic leukemias may possess steroid hormone receptors that can predict a high probability of response to the appropriate hormone when the receptor is present. The presence or absence of receptor may also be an important prognostic variable and may aid in the selection of patients for appropriate adjuvant therapy. Although putative receptors have been described in many other tumors, their clinical significance is questionable because these tumors generally do not respond to hormonal therapy. In the future, steroid receptors may enable us to target drugs, radioisotopes, or other molecules to tumors by linking these drugs to steroid hormones.