OBJECTIVE To investigate immunodominance in CD8+ T cell responses to human immunodeficiency virus type 1 (HIV-1) epitopes. METHODS Frequency of Interferon-gamma (IFN-gamma) secreting cells and the proliferation percentage of CD8+ T cells in PBMC from an HIV-1-infected long term nonprogressor (LTNP) were assessed after stimulation with either the 34 pools of 701 overlapping peptides covering the regions of HIV-1 Env, Pol, Gag, Vif, Nef, Tat or some single peptides, by using various assays including enzyme-linked immunospot (ELISPOT) and CFSE Carboxy-fluorescein diacetate, succinimidyl ester (CFSE) labeling and flow cytometry. RESULTS HIV-1 Gag peptides induced the highest frequency of IFN-gamma secreting cells, followed by Nef, Tat, and Vif. Meanwhile, Env and Pol failed to induce significant responses. In the IFN-gamma ELISPOT assay, stimulation with single peptide and the corresponsive peptide pool generated analogous results. In addition, the frequencies of IFN-gamma secreting cells and the proliferation percentage of CD8+ T cells detected-ELISPOT and CFSE labeling and flow cytometry were proportional, when single peptides were used for stimulation. CONCLUSIONS CD8+ T cells can respond to some specific HIV-1 epitopes and induce immunodominant responses. As a complimentary approach to the standard of ELISPOT assay, We recommend a novel CFSE labeling and flow cytometry assay for the examination of immunodominance in studies of HIV-1 specific proliferation percentage of CD8+ T cell responses.