Untreated malignant lymphatic system diseases are characterized by a preponderance of cell new formation (proliferation) against the destruction of lymphatic cells. If the lymph nodes are enlarged during these diseases, then cell new formation occurs largely or mostly in these lymph nodes. The proliferating cells of the lymph node are bigger than small lyphocytes and have, in general, a mean diameter of the nucleus of 10 mu and more. In normal lymph nodes they belong morphologically to the big lymphocytes, immunoblasts and plasmoblasts. In pathological lymph nodes they have to be looked for among the bigger cells of the disease-specific cell population. Whereas in healthy lymph nodes and in chronic lymphatic leukemia only about 1% of lymph node cells was found to proliferate, they amount on the average to 5% in lymphomas of lymphogranulomatosis and mostly to 30--50% in the lympho-reticulosarcoma (lymphoblast and immunoblast sarcoma, corresponding to large-cell, poorly differentiated lymphomas). The proliferating cells often appear as foci in the lymphomas. The generation times of the proliferating cells both in normal and pathological lymph nodes are about 24 hrs. or slightly longer. In lymphatic proliferation, apart from plasma cells big and smallymphocytes are produced in the normal lymph node; in CLL, big and small lymphocytes, in lymphogranulomatosis, big and small lymphocytes and Hodgkin-cells, and in poorly differentiated lymphomas, the corresponding lymphoma cells are produced. The clinicist is at the beginning of drawing conclusions from prevalent kinetic disturbances.