Plasma cell neoplasms often present in an asymptomatic, stable phase. Treatment should not be started until manifestations, such as bone pain, increased susceptibility to infections, renal failure, anaemia and weight loss, announce that the disease has progressed to the MM phase. Conventional therapy with melphalan and prednisone results in objective improvement in about 50% of patients and improves median survival to about 32 months from the start of treatment. Induction therapy should be continued until the M-protein reaches a stable plateau that lasts for at least 4 months. Maintenance therapy with melphalan prolongs the duration of the initial response, but does not improve overall survival, in comparison with patients receiving no maintenance therapy, because survival following relapse is shortened in those receiving maintenance melphalan. In two randomized clinical trials, maintenance treatment with interferon alpha prolonged remissions durations and overall survival of MM patients who responded to induction chemotherapy. Second-line treatment for MM patients who are primary refractory to melphalan, and for those who respond initially and then relapse with refractory disease, is outlined. Although long-term control is possible for a minority of patients, it is unlikely that MM can be cured with currently available chemotherapeutic agents. We need to learn more about the basic biology of the disease.