Fifty-three patients with multiple myeloma (MM) underwent an allogeneic stem cell transplant (HSCT) from their HLA identical siblings using a reduced-intensity conditioning consisting of thioteopa 5 mg/kg, fludarabine 90 mg/m(2), and melphalan 80 mg/m(2). Their median age was 52 years (range 38 - 68) and the interval from diagnosis 12 months. Forty-three patients (82%) had advanced disease and 33 had previously been treated with high-dose therapy with one (N = 21), or more (N = 12) autologus transplants. Ten (18%) had their allograft programmed after induction chemotherapy. The majority (N = 44) received peripheral blood as stem cell source. Acute graft-versus-host disease (GVHD) grade II - IV developed in 45%, but grade III - IV in only 5%. Cumulative incidence of chronic GVHD was 64%. Sixty-two per cent were in complete remission (CR) following transplantation. Transplant-related mortality was 13%. Relapse incidence was 32%. With a median follow-up of 22 months, 3-year overall survival is 45% and progression free survival (PFS) 37%. The thiotepa, fludarabine, and melphalan conditioning regimen can produce remissions in the majority of MM patients with a limited transplant mortality rate. When used as first line treatment the results of transplantation appear even more encouraging.