In this study, we aimed to measure P-glycoprotein (P-gp) expression in CD8(+) T lymphocytes of HIV-1-infected patients, to investigate how P-gp levels are affected by antiretroviral therapy (ART) in HIV-1 infection, and to assess the value of using P-gp expression to predict virologic response to ART. Peripheral blood mononuclear cells (PBMCs) were obtained from a cohort of HIV-1‑infected patients in China: 140 patients on ART, and 49 ART-naïve patients. We also enrolled 24 healthy blood donors as the controls. The expression levels of P-gp in CD8(+) T cells of HIV-1-infected patients were evaluated by quantitative reverse transcription PCR, ELISA and flow cytometry. A high inter-individual variability was observed in the CD8(+) T cells of both HIV-1-infected patients and healthy donors; however, the expression levels of P-gp were significantly higher in the HIV-1-infected group on ART compared to the ART-naïve group. The relative proportion of P-gp(+)CD8(+) T cells inversely correlated with the blood CD4(+) T cell count in the HIV-1‑infected patients on ART (r=-0.3343, P=0.0375). Groups of both good and poor responders showed significantly elevated levels of P-gp(+)CD8(+) T cells. The percentage of P-gp(+)CD8(+) T cells appeared to provide a sensitive estimate of the virologic response to ART compared to the CD4(+) T cell count. Our results suggest that P-gp expression varies among HIV-1‑infected patients, but is significantly higher in HIV-1‑infected patients on ART. The overexpression of P-gp is involved in ART initiation during HIV-1 infection, and P-gp(+)CD8(+) T cells may be an additional criterion for the evaluation of the antiretroviral response to ART.