The classification of malignant lymphoma is an important factor in treatment. Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL) should be clearly differentiated from each other, since their clinical behavior and response to treatment are quite different. Although four histological subtypes of HD has been recognized, the subclassification is not so important clinically. Many classifications of NHL have been devised, but most of them are based on morphological features only and do not incorporate recent advances in understanding of origin, function and differentiation of lymphoma cells. Further improvement is necessary to establish a reproducible, histogenetically accurate and clinically meaningful classification.