Although B-CLL is a hematological disorder characterized by clonal proliferation of B-cells, in most cases an increase in absolute numbers of T cells is observed. This increase is probably polyclonal in nature, since most data indicate that T lymphocytes are not progeny of the malignant clone in B-CLL. As CD4, CD8 and NK cells correspond to heterogeneous populations, in this work we tried to better define these subpopulations. Thus, CD4 subpopulations were displayed by using double labelling techniques into helper inducer subset (CD4+CDW29+) and suppressor inducer subset (CD4+CD45R+). CD8 subpopulations were delineated according to density expression of CD8 and reactivity with CD16 and CD11b in: suppressive cells defined by high density (HD) CD8 and reactivity with CD11b; NK cells defined by low density (LD) CD8 and binding to CD16; CTL cells by LD or HD CD8 and absence of expression of CD16 and CD11b. Our results concerning 47 normal control donors and 27 B-CLLs indicated that: although percentages of cells expressing CD3, CD4, CD8 and NK markers are decreased, absolute values of these subpopulations were increased; there exists an imbalance concerning CD4 and CD8, given by a more important increase of CD8 than CD4 subpopulations, but both are significantly augmented when compared to the normal range; within CD4 subpopulations, there is an important increase of CD4 CDW29 subset (helper inducer) whereas the CD4 CD45R (suppressor inducer) is not augmented in stage A patients and decreases in stage C patients; all the 3 identified CD8 subpopulations (NK, suppressors and CTLs) appeared to be increased; in 3 cases of clonal remission CLL studied, all T cell and NK subpopulations were recovering to normal percentages.