The biological features of tumour type, histological grade, vascular invasion, mitotic index, DNA index, and oestrogen receptor (ER) and progesterone receptor (PgR) status have been investigated as prognostic factors in primary operable breast cancer. We have studied these 7 factors in locally advanced primary breast cancer (LAPC): these patients have occult metastases at presentation. Of 60 consecutive patients presenting with locally advanced disease, 36 were treated initially with Tamoxifen and 24 by radiotherapy. Treatment failure was followed by cross-over to the other therapy. All patients were assessed for response in the primary tumour; external review of response was obtained. Survival was compared using the generalised Wilcoxon test. Response to therapy correlated significantly with histological grade (p = 0.02), ER (p = 0.02), PgR status (p = 0.02), mitotic index (p = 0.01), and tumour ploidy (p = 0.04). Survival from initial therapy correlated significantly with ER (p = 0.01) and PgR status (p = 0.04). Histological grade, mitotic index, tumour ploidy, and ER and PgR status of the primary tumour predict response and prognosis in patients with locally advanced (stage III) breast cancer.