DISEASE CHARACTERISTICS: Histologically proven multiple myeloma Initial diagnosis must have been confirmed by one of the following prior to initial treatment for multiple myeloma: Biopsy of an osteolytic lesion or soft tissue tumor composed of plasma cells Bone marrow aspirate and/or biopsy demonstrating at least 10% plasmacytosis Bone marrow containing less than 10% plasma cells but with at least 1 bony lesion and the M-protein criteria outlined below Measurable serum M-component of IgG, IgA, IgD, or IgE at initial diagnosis OR If only light chain disease (urine M-protein only) present, then the urinary excretion of light chain (Bence Jones) protein must have been at least 1.0 g/24 hours at time of initial diagnosis Must have undergone autologous stem cell transplantation within 1 year of beginning initial chemotherapy for multiple myeloma Must be randomized 60-100 days after autologous stem cell infusion No evidence of progressive disease