A 44-year-old woman with bone marrow metastasis from breast cancer was treated with weekly paclitaxel therapy. She underwent radical mastectomy for right breast cancer (T2N1M0, Stage II B) in April 2003, and was then treated with hormonal therapy (leuprorelin). In November 2005, she received radiation for bone metastasis in thoracic and lumbar vertebrae, and bisphosphonate therapy was performed. Additional hormonal therapy (tamoxifen) was administered for progressive bone metastasis. However, in September 2006, pancytopenia was recognized and bone marrow metastasis was diagnosed by bone biopsy. Disseminated intravascular coagulation (DIC) developed, so she was given weekly paclitaxel therapy with blood transfusion and G-CSF injection. Improvement of pancytopenia and tumor markers was recognized temporarily, and but 3 months later the tumor markers increased again. Four months after introduction of chemotherapy, she died of gastrointestinal hemorrhage.