The impairments in immune cell functions as well as changes in cytokine network are the cause of malignant cell accumulation and secondary immune deficiencies in B-cell chronic lymphocytic leukemia (B-CLL). To broaden the knowledge of immune system in B-CLL we tried to evaluate the Th1/Th2 and Tc1/Tc2 balance in B-CLL patients in comparison with healthy individuals and changes of this pattern during disease progression. The three-color flow cytometry technique was used to analyze IL-4 and IFNgamma expression in peripheral blood CD3+CD4+ and CD3+CD8+ cells. The results indicate the dominance of T type 1 cells and T-cell-mediated immunity in B-CLL patients that is however shifted towards T type 2 during disease progression.