The analysis of receptors for oestrogen in early cancer of the breast may be used to predict prognosis. The presence or absence of oestrogen receptors is independent of menstrual status, the stage of the patient's disease, and the histological grade of the tumour. Therefore combination with other prognostic factors gives a more accurate assessment of an individual patient's outlook. In the study described prognostic subgroups were determined from tumour axillary lymph node histology and oestrogen receptor status. The clinical application of these findings is discussed.