Adhesiveness of myeloblasts, promyelocytes, myelocytes, metamyelocytes, bands and polymorphonuclear neutrophils (PMN's) from the blood of patients with chronic granulocytic leukemia (CGL) was studied The adhesiveness of the cells to the substrate (glass) was tested In the presence of protein under dynamic conditions, i.e. when the suspension of cells was flowing over the substrate. It was found that adhesiveness of the CGL granulocyte precursors increased with maturation except for the myeloblasts. They exhibited a greater adhesiveness than the more mature promyelocytes. Changes in the physical and chemical parameters of CGL granulocytes occurring during maturation are discusses in the aspect of their adhesiveness.