The oestrogen (ER) and progesterone receptor (PR) status in a series of 281 women with breast cancer (followed up for a mean of 8.5 years) was correlated with eight histological variables, seven nuclear morphometric factors and two mitotic indices. Sex steroid receptor status was not significantly related to tumour size, axillary lymph node status or tumour recurrence. Sex steroid receptors were related to histological grade (P less than 0.0001), nuclear grade (P less than 0.0001), tumour necrosis (P = 0.0003), tumour circumscription (P = 0.0027), inflammatory cell reaction (P = 0.007), intraductal growth pattern (P = 0.0378), and tubule formation (P = 0.0432). Receptor status was also significantly related to nuclear morphometric variables (P less than 0.001) and mitotic indexes (P less than 0.001). In univariate analysis, ER (P = 0.2) and PR (P = 0.1) negatively predicted the recurrence free survival. Cancer related survival was predicted by ER (P = 0.0068) and PR (P = 0.0027). In small (diameter less than or equal to 2 mm) axillary lymph node negative tumours, ER (P = 0.09) and PR (P = 0.1) had some value in predicting the survival. The survival advantage of steroid receptor positive tumours was not due to adjuvant hormone therapy. Sex steroid receptors had independent predictive value in multivariate survival analysis and also in small (diameter less than or equal to 20 mm) tumours. The results indicate that sex steroid receptor negativity is related to several malignant histological features in breast cancer and hormone receptors have prognostic value. Their prognostic influence seems to be mediated through the different proliferation rates in receptor positive and negative breast carcinomas.