Results from a previous longitudinal study, the Swedish OCTO-Immune study, indicated that the combination of higher CD8 peripheral blood lymphocytes (PBLs), decreased CD4 PBLs, and poor proliferative response to mitogenic stimulation in very old humans were associated with an increased 2 year mortality. In follow up studies this combination of immune parameters was significantly associated with a CD4/CD8 ratio less than one and positive IgG serologic titers to cytomegalovirus (CMV). The present study, the Swedish NONA-Immune study, was an extension of that study, using a new sample of the very old. The results of this study confirmed the results of the previous study and extended the surface marker profile of the PBLs, indicating that the CD4/CD8 ratio change is associated with increased CD8 cells, decreased CD4 cells, and lymphocyte activation. The predominant phenotypes of the CD3+CD8+ cells were CD27-, CD28-, CD56+, and CD57+, CD45RA+, and double marked CD45RA+RO+. As in the OCTO study, the NONA-Immune data indicated that the changes are associated significantly with seropositive responses to CMV.