Estrogen and progesterone receptor determinations were performed on 518 specimens at the Surgical Research Laboratory of the Maimonides Medical Center. Of these, 41% were ERP and PgRP positive; 17% were ERP positive and PgRP negative; 38% were ERP negative and PgRP negative, and 3.9% were ERP negative, PgRP positive. Sixty-two patients with advanced breast cancer were treated with either an endocrine ablative procedure or with antihormonal therapy. In the two treatment groups the overall response rate when both receptors were positive was 79%, with a higher percentage of responders in the endocrine ablative group (88% vs. 69%). In addition, a greater duration of response was achieved in those patients treated with endocrine ablation. The overall predictability of response was achieved in those patients treated with endocrine ablation. The overall predictability of response or failure to hormonal therapy is 91% if the progesterone receptor alone is utilized to select treatment and an endocrine ablative procedure is performed. The predictability of response based on the estrogen receptors presence or absence is 70%.