DISEASE CHARACTERISTICS: Histologically proven relapsed or refractory, low grade or transformed low grade B-cell non-Hodgkin's lymphoma including the following: Small lymphocytic Follicular small cleaved cell Follicular mixed small cleaved and large cell (less than 50% large cell component) Tumor must be positive for CD20 antigen Relapse or disease progression following at least 1 chemotherapy regimen or failure to achieve an objective response (complete or partial response) on prior chemotherapy regimen No disease progression, within 1 year of irradiation, arising in a field previously irradiated with more than 3500 cGy Mean of no greater than 25% intratrabecular marrow space involved with lymphoma on bilateral iliac crest bone marrow biopsy A new classification scheme for adult non-Hodgkin's lymphoma has been adopted by PDQ. The terminology of "indolent" or "aggressive" lymphoma will replace the former terminology of "low", "intermediate", or "high" grade lymphoma. However, this protocol uses the former terminology.