Non-Hodgkin's lymphomas (NHL) represent a heterogenous group of diseases including low, intermediate and high grade histological subtypes. Most entities are sensitive to chemotherapy and radiotherapy. However, most relapsed patients are incurable with conventional treatment. The major reason for unsatisfactory long-term results in NHL is tumour cells that persist after standard treatment. New sensitive techniques have been developed to detect occult lymphoma cells. These cells might be eradicated by new immunotherapeutic agents with different modes of action, such as cytokines or antibody-based agents. In NHL, most experience has been accumulated with interferon-α, which seems to be effective against minimal residual disease (MRD). The experience with interleukin-2 and interleukin-3 is less convincing. Monoclonal antibodies have been used in their native form, or conjugated with radioisotopes or toxins to selectively destroy lymphoma cells. Such immunotoxins and radioisotope-coupled antibodies have shown promising results in early clinical trials, and are now being evaluated in patients with smaller tumour burdens.