comparable age, while finding no difference in plasma levels of androstenedione or testosterone.The present study was undertaken to measure by radioimmunoassay oestradiol-17/ in the serum of male breast-cancer patients to determine whether there was an excess of this oestrogen over normal controls of comparable age; also, to determine whether such an excess was elicited from the testis by an abnormal stimulation by LH and FSH, or whether the excess of oestrogen was transformed from a high level of its precursor, testosterone.During this study, 3 of the patients had biopsy specimens taken from skin metastases, and the tissue was then assayed for receptor sites for oestradiol-173 and progesterone. Leclereq et al. (1976) reported 6 out of 7 primary tumours in men with positive oestrogen-receptor activity, and one out of 3 patients with metastatic disease had receptor sites in tissue biopsy material.The investigations were performed on 10 men aged between 30 and 75 years with histologically proven carcinoma. Blood samples were taken before the start of primary treatment.Control studies were carried out on 31 men with a mean age of 61-9 years (range 37-89) who were free from any evidence of disease or history of chronic illness, and none of whom were taking any drugs, including hormones.Blood was collected in plain tubes,

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