Autologous hematopoietic cell transplantation (HCT) followed by nonmyeloablative allogeneic HCT (auto/alloHCT) provides cytoreduction and graft-versus-myeloma effects. We report on long-term outcomes of 102 patients with multiple myeloma who received auto/alloHCT with a median follow-up of 6.3 years. Treatment consisted of high-dose melphalan and autograft followed by 2-Gy total body irradiation, with or without fludarabine, and alloHCT from human leukocyte antigen-identical siblings. Postgrafting immunosuppressive agent was cyclosporine or tacrolimus and mycophenolate mofetil. Forty-two percent of patients developed grade 2 to 4 acute graft-versus-host disease (GVHD) and 74% extensive chronic GVHD. Five-year nonrelapse mortality after allografting was 18%, 95% related to GVHD or infections. Among 95 patients with detectable disease, 59 achieved complete remissions. Median time to progression was 5 years. Median overall survival (OS) was not reached. Median progression-free survival (PFS) was 3 years. Five-year OS and PFS were 64% and 36%, respectively. Seventy-three patients receiving autoHCT within 10 months from treatment initiation had 5-year OS of 69% and PFS of 37%. In multivariate analysis, beta-2-microglobulin of more than 3.5 microg/mL at diagnosis and auto/alloHCT more than 10 months after treatment initiation correlated with shorter OS (P = .03 and P = .02) and PFS (P = .04 and P = .03), whereas Karnofsky scores less than 90% at allotransplantation correlated with shorter PFS only (P = .005). Long-term disease control and GVHD remain key issues.