Decreased percentage of B cells expressing L-selectin in B-cell chronic lymphocytic leukemia (B-CLL) is known from literature. The purpose of our studies was to compare the intensity of L-selectin expression on subpopulation of L-selectin positive B-lymphocytes in untreated and treated patients with B-CLL. The lymphocytes were obtained from peripheral blood of 70 patients suffering from B-CLL (40 untreated and 30 after the treatment) and 20 healthy blood donors. The percentage of positive cells and intensity of CD62 L-selectin expression (RFI) were measured on CD19+ B lymphocytes using tri-color fluorochrom labeled monoclonal antibodies and flow cytometric analysis. The lower percentage of L-selectin positive B-cells paralleled with considerable decrease of this selectin intensity was observed in patients with B-CLL in comparison to healthy subjects. Both these changes may contribute to the impaired adhesion and migration of B-cells in B-CLL resulting in the accumulation of these cells in the peripheral blood. In a group of patients entirely responding to the treatment the tendency toward normalization of both measured parameters has been observed.