Both the magnitude and breadth of HIV-specific immunity were evaluated longitudinally on samples collected from six subjects starting highly active antiretroviral therapy (HAART) preseroconversion (group 1), 11 recently infected subjects starting HAART postseroconversion (group 2), five subjects starting HAART in the second half of the first year of infection (group 3), and six persons starting treatment in the chronic phase of infection (group 4). HIV-specific immunity was measured by IFN-gamma ELISPOT, detecting the frequency of cells responding to a panel of HLA-restricted HIV-1 peptides. Intracellular cytokine staining was used to detect the frequency of HIV-1 Gag p55-specific CD4(+) and CD8(+) T cells in a subset of participants. The magnitude and breadth of HIV-specific responses persisted in all group 1 subjects and in 5 of 11 (45%) group 2 subjects. Both of these parameters declined in 6 of 11 (55%) group 2 and in all group 3 and 4 individuals. All persons who maintained detectable numbers of HIV-1 Gag p55-specific CD4(+) and CD8(+) T cells after starting HAART preserved the intensity and breadth of their HIV-specific effector response. Our results show that HIV-specific immunity can be preserved even if HAART is initiated beyond the acute phase of infection.