Estrogen receptor (ER) status and urinary androgen (A) concentration were simultaneously determined in 50 premenopausal patients submitted to bilateral ovariectomy for advanced carcinoma of the breast. When both the hormonal parameters were positive (ER+ A+), the response to castration was favorable in 87.5% of the cases, with a survival rate of 39% at 5 years. No patient responded to the therapy when both the parameters were negative (ER- A-); none of them was alive at 5 years. An intermediate response (more than 50%) and survival rate at 5 years (more than 20%) was obtained in the group of patients with at least one of the two parameters positive (ER+ A-, or ER- A+). These responses were independent of the topography of neoplastic localizations and the length of the disease-free interval.