Optical mammography is a functional imaging technique that uses near-infrared light to produce three-dimensional breast images of tissue oxygen saturation and hemoglobin concentration. It has been used to monitor the response to neoadjuvant chemotherapy in breast cancer patients. We present the first results on monitoring tumor response to hormone therapy using optical mammography. We present three case studies from postmenopausal women treated with neoadjuvant hormone therapy for locally advanced breast cancer. The women were scanned before starting treatment, once during treatment, and then before surgery. Changes in physiological and optical properties within the tumor and in the rest of the breast were evaluated. At the time of surgery, two patients partially responded to treatment and one did not respond. The patients that partially responded on ultrasound revealed a corresponding recovery to normal in the hemoglobin concentration images, whereas the nonresponder indicated an increase in hemoglobin concentration in the tumor compared to her pretreatment images. These case studies suggest that optical imaging of the breast during neoadjuvant hormone treatment can provide potentially valuable information, and that physiological changes within the tumor can be seen in response to treatment.