A series of 208 breast cancer biopsies were analysed immunohistochemically for expression of E-cadherin (E-CD). Altogether, 72 per cent of the tumours showed E-CD positivity in over 50 per cent of cells, the staining being heterogeneous in nearly all tumours. In only 16 per cent of ductal carcinomas was positive staining seen in less than 1 per cent of cells. Expression of E-CD was not related to tumour diameter, nodal status, metastasis at diagnosis, histological grade, DNA ploidy, S-phase fraction, nuclear area, mitotic frequency, or PR content. There was a significant relationship between expression of E-CD, histological type (P = 0.01), the proportion of intraductal growth (P = 0.008), the density of tumour-infiltrating lymphocytes (P = 0.0007), ER content (P = 0.012), and morphometric nuclear factors (P < 0.02). Expression of E-CD showed a weak association with a high survival probability (P = 0.02), while the relation to recurrence-free survival was not significant (P = 0.1). In axillary lymph node-negative tumours, E-CD expression was not related significantly to survival (P = 0.11) or to recurrence-free survival (P = 0.06). In multivariate analysis, E-CD expression had no independent prognostic value, while the axillary lymph node status, tumour diameter, patient age, and mitotic frequency were independent prognostic factors. The results indicate that E-CD expression is related to several histological features in breast cancer, but has no independent prognostic value over standard prognostic factors.