Oestrogen receptor assay was performed on one hundred and sixty-eight patients with proven breast cancer. Fifty-two per cent were positive for receptors; there was a lower incidence of positives in both the pre- and postmenopausal women, when compared with corresponding figures for American women. Patients were randomized into different modes of treatment. It was found that oestrogen receptor positive patients fared better than the negative ones irrespective of the stage of the disease or the treatment received, and this difference was statistically significant in patients with early disease (stages one and two). In patients assigned to some form of endocrine manipulation, 77% of receptor positive, and 7% receptor negative patients showed a response to treatment; in those receiving chemotherapy, receptor negative patients fared better than the positive ones, though the difference was not statistically significant.