OBJECTIVES: I. Assess bone marrow reconstitution and peripheral blood cell counts of patients with multiple myeloma treated with high-dose melphalan (L-PAM) and total-body irradiation (TBI) followed by peripheral blood stem cell (PBSC) rescue. II. Assess the efficacy of intravenous L-PAM and TBI for treatment of relapsing/refractory myeloma. III. Assess the tolerability and toxicity of this regimen in patients with relapsing multiple myeloma. IV. Assess response rate and survival of relapsing/refractory patients treated with this regimen.