Overexpression of erbB2 in breast tumours can predict resistance to tamoxifen therapy. We conducted a small trial to determine if erbB2 status correlates with tumour response and biochemical changes in postmenopausal women receiving neoadjuvant therapy with the aromatase inhibitor, anastrozole. Twenty-four postmenopausal women with oestrogen receptor (ER)-rich, large, operable breast tumours received three months of neoadjuvant anastrozole, 1 or 10 mg daily, then surgery, followed by another five years of anastrozole 1 mg daily. Response to the treatment was based on changes in clinical and ultrasound measurements of tumour volume and changes in tumour proliferation and progesterone receptor (PgR) status. After follow-up for a median duration of four years therapy, there was no apparent difference between erbB2 0/1+ and erbB2 3+ tumours in clinical response or changes in proliferation and PgR expression. In conclusion, anastrozole appears to be an effective endocrine option in this patient population, irrespective of the erbB2 status.