Iron is a key factor at various stages of HIV life cycle and determines the progression of HIV infection. Data about cellular labile iron pool (LIP) in the settings of contemporary antiretroviral therapy (cART) are lacking. Yet LIP is directly related to the generation of reactive oxygen species, and may contribute to immune activation, dysfunction, and exhaustion. Using multiparameter flow cytometry, we evaluated LIP in CD4 and CD8 T cells from HIV+ patients with sustained viral suppression (SVS) as a result of continuous long-term cART. Based on the recovery of CD4/CD8 ratio, two patients' subgroups were defined: A (n = 26), CD4/CD8 > 0.9, and B (n = 37), CD4/CD8 < 0.9, with significantly differing CD4 absolute count (AC) (mean 752 vs. 571 cells/μL, p < .05). Although hemoglobin and serum iron had recovered in all patients, CD4 T cell LIP and CD8 T cell LIP were significantly higher than that of controls, both in the subgroup with complete (A) and with incomplete (B) immune recovery [mean CD4 mean fluorescence intensity (ΔMFI) 318.7 and 777.8 vs. 157.6; mean CD8 ΔMFI 359.5 and 628.7 vs. 179.2, analysis of variance p < .05 for both]. CD4 LIP correlated inversely with CD4 AC (R = -0.4, p < .01), and both CD4 LIP and CD8 LIP-with CD4/CD8 ratio (R = -0.4, p < .01). Thus, increased CD4 T cell LIP and CD8 T cell LIP in the settings of SVS and immune recovery are a sensitive marker of residual immune activation and may predict immune exhaustion in long-term cART-treated patients.Keywords: HIV; T lymphocyte subsets; cART; labile iron pool.