Advances in the development of monoclonal antibodies have led to new agents rapidly incorporated into standard lymphoma therapy. The characteristics of the target antigen and the properties of the antibody including interaction with the host immune system have been found to correlate with outcome. Antibodies targeting the CD20 antigen on B cells have been most widely used, led by the chimeric antibody rituximab, now used in nearly all types of B-cell non-Hodgkin's lymphoma (NHL). New antibodies targeting CD20 with augmented complement or Fc receptor binding are now being evaluated and will eventually have to be compared with rituximab. Challenges to these new antibodies include the nearly universal use of rituximab early in NHL therapy, and its increasing use as maintenance therapy. It is not clear what the activity of these antibodies will be in rituximab-refractory patients. New antibodies targeting antigens such as CD40 and CD80 are also being tested alone and in combination with rituximab. Vaccine trials using patient-specific immunization with immunoglobulin idiotype (Ig-Id present on the surface of most B-cell NHL) isolated by molecular rescue or by cell hybridization techniques are also nearing completion. These approaches attempt to actively induce specific humoral or cellular immune responses to the Ig-Id by attaching the protein to a carrier protein and the use of an immunologic adjuvant such as granulocyte macrophage colony-stimulating factor. Prior rituximab appears to delay humoral responses to the idiotype but may still allow cellular responses. The incorporation of all these approaches into optimal NHL therapy remains a challenge.