Patients with multiple myeloma must be differentiated from those with monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). The plasma cell labeling index is helpful in differentiating MGUS or SMM from multiple myeloma (MM). No difference in survival was noted between patients given a single alkylating agent and those given a combination of alkylating agents. Alternating cycles of interferon alpha 2 and VBMCP (vincristine, BCNU, melphalan, cyclophosphamide, prednisone) produced a complete or near-complete response in 41% of patients. Allogeneic or syngeneic bone marrow transplantation has produced some benefit. Autologous bone marrow transplantation is potentially applicable to treat more patients. Major problems are eradication of myeloma cells from the bone marrow and removal of myeloma cells from autologous bone marrow. Purging of myeloma cells with monoclonal antibodies and chemotherapy may be helpful. Stem cells from autologous peripheral blood are being used for rescue after high-dose chemotherapy and total-body irradiation.