A 66-year-old postmenopausal woman presented in June 1991 with a giant ulcerated left breast tumor. She had discovered the tumor two years previously, but had never visited any medical institution. She was diagnosed as advanced breast cancer with multiple lung metastases, bone metastasis, and both supraclavicular lymph node metastases by physical examination, fine needle aspiration cytology, chest X-P, and bone scintigraphy. Incisional biopsy, performed to confirm the histological type of breast cancer and to evaluate estrogen and progesterone receptor (ER and PgR) status, revealed solid-tubular carcinoma. Both ER and PgR were highly positive at 322.6 and 228.0 fmol/mg protein, respectively. Therefore, endocrine therapy was chosen to treat this advanced breast cancer patient, although she had multiple organ metastases. Twenty mg of Tamoxifen a day was administered per os. After treatment with tamoxifen, the size of ulceration started to decreased and the dyspnea caused by multiple lung metastases was reduced. Eight weeks after, she showed partial response (PR) determined from the size of the ulceration and chest X-P. She has been maintaining PR for more than 9 months. Thus, Tamoxifen was shown to be very effective for this case of advanced breast cancer with multiple organ metastases.