Summary Sixty patients with locally advanced breast cancer, but with no evidence of distant metastases were randomised to receive primary endocrine therapy or chemotherapy after assessment and 'Trucut' biopsy of the primary tumour. After 12 weeks all patients were assessed. Eight out of 30 (27%) of the patients who received chemotherapy showed complete clinical regression of the primary cancer, eight patients' tumours had regressed by more than 50%, and ten showed a 25-50% reduction in bi-dimensional diameter. Only four (13%) patients' tumours failed to reduce in size. Seven patients were judged to require mastectomy at the end of the 12 week period of treatment with chemotherapy. In contrast, only three out of 30 (10%) patients receiving endocrine therapy showed a greater than 50% reduction in tumour size, and four patients had a 25-50% reduction at 12 weeks. The remaining patients' tumours either stabilised (12 patients) or enlarged (II patients). We conclude that primary chemotherapy in patients with primary breast cancer is more effective in rapidly reducing the size of the primary breast cancer than endocrine therapy (P = 0.001) and alters significantly the future management of these patients. However, at 65 weeks on completion of the follow-up, there is no significant difference in the number of patients' disease-free, locally or distant recurrent, or dead.