Patients suffering from bronchogenic and gastrointestinal cancer without, as well as with metastases, were investigated to provide more information on the number of morphology of lymphocytes in their peripheral blood particularly in respect to the frequency of various nucleolar types in these cells. The decreased number of lymphocytes in the peripheral blood of the cancer patients was due to the decline of lymphocytes with ringshaped nucleoli representing resting cells which can be stimulated in respect to the RNA synthesis and blastic transformation. The decreased number of such cells was apparently more pronounced in the peripheral blood of the patients suffering from gastrointestinal cancer with metastases. The increased frequency of lymphocytes with compact nucleoli or nucleoli with nucleolonemas representing immature or stimulated cells was noted in most patients suffering from bronchogenic cancer without, and with metastases in lymph nodes, as well as in some patients with gastrointestinal cancer and, without metastases. On the contrary, the decreased number of these cells was observed in the peripheral blood of patients suffering from gastrointestinal cancer with metastases. All these changes provide further information on the changes of the lymphocytes in the peripheral blood of the patients suffering from malignant disease. The possible interpretation of these changes presented in the discussion is in accordance with the present conception on the relationship between the malignant growth and lymphocytes.