Eribulin mesylate, a novel microtubule inhibitor with a unique mechanism of action, was approved in Japan in April 2011 for the treatment of metastatic breast cancer patients who had been administered at least two prior chemotherapeutic agents. Here, we present a retrospective review of data from 27 patients who received eribulin monotherapy in our hospital. The overall response rate and clinical benefit rate were 25. 9% and 29. 6%, respectively, and the median progression-free survival was 9. 9 weeks(95% CI: 3. 5-16. 2 weeks). The toxicities of treatment were tolerable and manageable; responses were lower in patients who were triple negative subtype, and higher in patients who had responded to prior taxane treatment. The relative dose intensity of our data indicates that appropriate modification of dose and schedule may be an important part of eribulin monotherapy.