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INTRODUCTION Quantification of lymphocyte subpopulations is useful for evaluating immune response in states of health and disease, including immunodeficiencies, autoimmunity, infections and cancer. Studies have found that concentrations and proportions of different cell subpopulations vary with geographic location, age, sex and ethnicity. Knowing the normal values of these cells and their variation in healthy populations will contribute to improved clinical practice and scientific research. OBJECTIVE Estimate normal absolute concentrations and percentages of the most abundant lymphocyte subpopulations in peripheral blood and their relation to sex and age. METHODS A cross-sectional analysis was conducted in 129 healthy adults, 61 men and 68 women aged 18-80 years; 89 aged <50 years and 40 ≥50 years. We included individuals who agreed to participate by written informed consent. Exclusion criteria were chronic disease, or use of tobacco, alcohol or medications that can alter immune system cell numbers and functions. Through dual platform flow cytometry, we determined absolute and percentage values for T lymphocyte subsets CD3+, CD3+/CD4+T, CD3+/CD8+T, CD19+ B cells and CD3-/CD56+ natural killer cells in peripheral blood, using an 8-color flow cytometer. We estimated medians and the 2.5 and 97.5 percentiles and calculated the Pearson correlation coefficient to evaluate associations. Significance tests were also used to compare groups. The significance threshold was p = 0.05 in all cases. RESULTS Ranges of absolute values and percentages (%) were: total lymphocytes: 1200-3475 cells/μL (20.2-49.3); CD3+ T cells: 880-2623 cells/μL (56.5-84.7); CD3+/CD4+ T cells: 479-1792 cells/μL (30.3-55.7); CD3+/CD8+ T cells: 248-1101 cells/μL (13.2-42.9); CD19+ B cells: 114-1491 cells/μL (5.4-49.5); CD3-/CD56+ natural killer cells: 70-652 cells/μL (3.7-28.0); and the CD4+:CD8+ index: 0.80-3.92. Absolute numbers--but not percentages--of lymphocytes and CD3+ T cells were higher in those <50 years (p = 0.025 and 0.020, respectively). Absolute values and relative percentages of CD3+/CD8+ and relative values of CD3+/ CD4+ T cells were significantly higher in the younger subgroup (p = 0.004 and p = 0.047). Age was not associated significantly with B lymphocytes or natural killer cells. Absolute and relative values of CD3+/CD4+ T lymphocytes were significantly higher in women (p = 0.009 and 0.036, respectively). CONCLUSIONS. Absolute numbers of total lymphocytes and T and CD3+/CD8+ T lymphocytes are higher in younger individuals. In percentage values, CD3+/CD4+ T lymphocytes are lower in older persons. Absolute and percentage values of CD3+/CD4+ T phenotype are higher in women. These differences justify adjusting clinical analyses to different values by age and sex. KEYWORDS T lymphocytes, B lymphocytes, normal values, flow cytometry, age, sex, Cuba.