The epidermal growth factor receptor (EGFR) is a therapeutic target in a number of settings in solid malignancies, but its role in breast cancer has remained unclear and controversial. In 810 primary breast cancers derived from patients suitable for cytotoxic chemotherapy, EGFR was prospectively measured and interactions with tumour and clinical correlates were tested to observe whether postulated cross-talk mechanisms are likely to modulate breast cancer metastasis and proliferation. A minority (79 tumours, 9.8%) were EGFR positive; in a multivariate analysis the likelihood of being EGFR positive was significantly increased for patients with grade 3 disease, compared with grade 1 (OR 15.6; 95% CI 2 to 122, p=0.0001), and for oestrogen receptor-negative status compared with positive (OR 24.1; 95% CI 12.7 to 46.00, p=0.0001). EGFR expression may play a role in breast cancer proliferation, but appears unlikely to modify tumour pathology via postulated mechanisms of oestrogen receptor/EGFR-mediated cross-talk.