Background Man who has sex with man (MSM) is one of the high risk groups for spreading HIV/AIDS. It was reported that the most prevalent human immunodeficiency virus type 1 (HIV-1) strain among MSM is subtype B; however, T cell immunity remains unknown across the HIV-1 B genome in this population.Methods Using Elispot assay with synthetic peptides spanning the sequence of HIV-1 consensus B,HIV-1-specific cytotoxic T-cell lymphocyte responses were quantified among 3 treated and 19 untreated HIV-1 infected MSM from Beijing, China. Cross-sectional association between viral loads and cellular immune responses were analyzed.Results Peptide pools corresponding to each HIV-1 protein were used for Env, Gag, Pol, Nef, Tat/Rev, Vpr/Vpu and Vif. The results showed that the magnitude of T cell responses in the 3 treated HIV+ MSM group [median,770 spot forming cells (SFCs) per 106 peripheral blood mononuclear cells (PBMCs)] might be significantly lower than that in the 19 untreated HIV+ MSM group (median, 6175 SFCs per 106 PBMCs). Nef, Gag and Pol are the most frequently targeted HIV-1 antigens; and 16 subjects (73%) were identified with vigorous T cell immunity against each of these three proteins. The overall magnitude of T cell immunity closely related to its breadth (r=-0.72, P＜0.05) and was inversely but weakly associated with viral loads (r=-0.15). Further analysis showed that both Gag (r=-0.24) and Pol specific T cells (r=-0.12) contributed to this inverse association whereas Nef specific T cells showed no association with viral loads.Conclusions The magnitude of HIV-1 specific T cells is inversely but weakly associated with viral loads among MSM; HIV-specific T cell responses against conservative sequences (Gag and Poi) are the main contributors to this association among Chinese HIV+ MSM. These findings have important implications for vaccine design.