Previous studies have shown that CD8 cell subsets, some expressing activation markers, are elevated in human immunodeficiency virus (HIV) infection. To assess the overlap of these subsets, we used three-color flow cytometry to phenotype CD8 cells in cryopreserved mononuclear cells from uninfected controls and from people infected with HIV, in CDC classes II, III, and IV (n = 12 per group). There were several CD8 subset changes observed in association with HIV infection. A shift from a naive (CD45RA+CD45RO-) to a memory (CD45RA-CD45RO+) phenotype occurred in the CD8 subset, but the intermediate phenotype (CD45RA+CD45RO+) was unchanged. Increases in DR+CD8 and CD38+CD8 cells were noted in both naive and memory CD8 subsets, defined by CD45RA or CD45RO expression. Both the CD57+ and CD57- subsets of DR+CD8 cells were increased, whereas only the CD57+ subset of CD38+CD8 cells was elevated. The increase in CD57+CD8 cells reflected a selective rise in CD57+CD8 cells coexpressing CD38, DR, and CD45RO. The CD38+ DR+ CD8 subset was markedly increased and was apparently derived from both the CD38-DR-CD8 and CD38+DR-CD8 subsets. Compared with classes II and III, the CDC class IV group showed an increased proportion of CD8 cells expressing CD38; higher percentages of CD38+DR+CD8, CD38+CD45RA-CD8, and DR+CD45RO+CD8 subsets; and decreased percentages of CD38-CD45RA+CD8 and CD38-CD57-CD8 cells.(ABSTRACT TRUNCATED AT 250 WORDS)