We show that the fraction of proliferating CD4⁺ lymphocytes is similar in HIV-infected subjects in the early stage of disease and in HIV-negative subjects, whereas the fraction of proliferating CD8+ lymphocytes is increased 6.8-fold in HIV-infected subjects. After initiation of antiviral therapy, there is a late increase in proliferating CD4⁺ T cells associated with the restoration of CD4⁺ T-cell counts. These results provide strong support for the idea of limited CD4⁺ T-cell renewal in the early stage of HIV infection and indicate that after effective suppression of virus replication, the mechanisms of CD4⁺ T-cell production are still functional in early HIV infection.