The non-Hodgkin's lymphomas are a group of diseases for which substantial progress has been made in understanding tumor biology and effectiveness of treatment during the last decade. These advances may provide insight into the development of neoplasms because of recognized association of lymphomas with viral infections and immunodeficiency. The prognosis for patients with NHL continues to improve. As a result, current studies on treatment of lymphomas in certain favorable stages have concentrated on reducing the intensity of therapy. For patients with advanced disease, further improvements in treatment are still being sought.