A 34-year-old man was diagnosed as having solitary testicular plasmacytoma. He had received palliative radiotherapy, several combined chemotherapies including CHOP chemotherapy (vincristine, cyclophosphamide, Adriamycin, and prednisone), MP (melphalan and prednisone) and M-2 protocol (melphalan, prednisone, vincristine, carmustine, and cyclophosphamide), and interferon therapy as 3 million units subcutaneous injection three times a week for 1 year. Extensive bone plasmacytoma developed 7 years later without bone marrow involvement. We suggest that early use of combined chemoradiotherapy and high-dose chemotherapy with autologous stem cell support should be investigated in patients with testicular plasmacytoma with dissemination.