The phenotypic reconstitution of lymphoid cells in the bone marrow and peripheral blood was examined prospectively in 27 patients who underwent autologous bone marrow transplantation (ABMT) for leukemia/lymphoma. Patterns of activation within NK and T cell subsets as well as T sub-subsets were studied with monoclonal antibodies in two- and three-color FACS analysis. NK-like cells (CD16+) were found to be increased in the peripheral blood and bone marrow after ABMT. The expression of two activation markers, 4F2 and HLA-DR, was sustainedly increased within this subset. High numbers of CD4+ and CD8+ T cells carrying surface HLA-DR were found early after ABMT both in blood and marrow. The T suppressor inducer cell sub-subset (CD45R+ CD4+) was severely depressed in both the blood and marrow 6-9 months post-ABMT. Using three-color FACS analysis, half of this T sub-subset was shown to express HLA-DR+. The levels of T suppressor effector-like cells (CD11+ CD8+) remained within the normal range in both peripheral blood and bone marrow during follow-up. The HLA-DR expression was elevated and equally distributed between the CD11- CD8+ and CD11+ CD8+ sub-subset cells. There was no major impact of marrow T cell purging or CMV carrier status on the phenotypic NK/T cell reconstitution. The present results provide an immune phenotypic basis for the suggested generation of anti-leukemic NK-like and T suppressor-like activity after ABMT.