There is sufficient evidence to support both the hormonal influence on the outcome of breast cancer surgery and the SDA hypothesis. The SDA model produces a paradigm shift in the understanding of the natural history of breast cancer. It offers opportunities to try modifying a tumor's biological potential for metastasis (e.g., by tamoxifen, progesterone, antiprotease, or angiostatin) in the neoadjuvant setting. It continues to support the beneficial effects of detection and surgery early in the natural history of disease. It would be worthwhile to plan a trial comparing standard practice (unplanned surgery as the patient enrolls) with surgery during the luteal phase of the menstrual cycle in premenopausal women. Another possibility, based on studies of circulating progesterone, would be to compare primary progesterone treatment (for 4 to 10 days before surgery) with standard practice. Such a trial of primary progesterone is already under way, conducted by the Indian Breast Group. More than 200 patients have enrolled so far. The details of the trial are available from Clinical Research Secretariat, Tata Memorial Centre, Parel, Mumbai, India (e mail: tmho3@bom2.vsnl.in).