DISEASE CHARACTERISTICS: Histologically confirmed B-cell non-Hodgkin's lymphoma (low, intermediate, or high grade categories) Must have been treated with chemotherapy and/or radiotherapy with evidence of minimal residual disease by conventional diagnostic modalities 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.