Ferritin levels in blood serum and mononuclear cells of the peripheral blood were determined in 60 patients with chronic lymphatic leukemia (group I), and 31 patients with other lymphomas of the low and medium degree of malignancy (group II). Significantly higher blood serum and mononuclear cells ferritin was found in the examined patients than in 54 healthy individuals. Particularly high ferritin levels were seen in blood serum of patients of group II in whom clinical stage of the disease was high. Moreover, moderate correlation of ferritin content in mononuclear cells and absolute leucocytosis was found in group I. This parameter correlated well with the percentage of poorly differentiated cells (group II).