We report the case of a 54-year-old female patient with stage IIIA kappa light chain myeloma (MM) who relapsed 7 years after syngeneic bone marrow transplantation (BMT). The relapse occurred as a voluminous soft tissue plasmacytoma in the leg, developing after local trauma. The patient was successfully treated with local radiotherapy and has remained progression-free for more than 2 years. This case represents one of the longest survivors, in complete remission, after syngeneic transplantation for MM. The presentation of recurrent disease as localized plasmacytoma with extramedullary growth is unusual in the post-transplant setting. Bone Marrow Transplantation (2000) 25, 115-117.