Immunotherapy. Neuroblastoma as a model. Combinations of aggressive therapy and radiotherapy directed at the primary tumor site as well as dose intensive chemotherapy against metastases can effectively induce complete remissions in patients with stage IV neuroblastomas. By virtue of its tumor specificity, the use of immunotherapy at the time when microscopic residual disease is present holds great promise in eradicating the tumors permanently. Monoclonal antibodies can accumulate selectively and at high concentrations in neuroblastomas. They have the potential of initiating complement activation and inflammation at the tumor site. Hematopoietic factors and cytokines can reinforce the body with tumoricidal leukocytes. Ex vivo activation of autologous white cells as well as arming by genetic manipulation can also produce tumor-seeking vehicles that may be therapeutically useful. As the knowledge of tumor and host immunobiology accumulates, the optimal combination of these approaches will become apparent. 