A 63-year-old female with relapsed and refractory multiple myeloma, in whom the duration of disease and history of chemotherapy were 15 years and 9 years, respectively, was treated with bortezomib and dexamethasone. A very good partial response and about 500 days to progression were obtained at a total dose of 10.2 mg bortezomib, until the day 4 injection of the second course. Bone pain has completely disappeared. These findings suggested that the therapeutic efficacy of bortezomib may persist over a long period regardless of the duration of chemotherapy. When a favorable response is obtained, but continuous therapy with bortezomib is difficult for reasons such as adverse events (other than refractory to bortezomib), careful observation may be one of the important options.