A survey was carried out on 150 healthy adults to establish hematological reference ranges for human immunodeficiency virus (HIV)-negative adults from the Central African Republic (CAR). Immunohematological mean values, medians, and 95th-percentile reference ranges were established. Mean values were as follows: leukocyte (WBC) counts, 5.28 x 10(9)/liter (males) and 5.11 x 10(9)/liter (females); erythrocyte counts, 5.20 x 10(12)/liter (males) and 4.50 x 10(12)/liter (females); hemoglobin, 15.1 g/dl (males) and 12.5 g/dl (females); hematocrit, 45% (males) and 37% (females); lymphocytes, 2,587/ micro l (males) and 2,466/ micro l (females); CD4 T cells, 927/ micro l (males) and 940/ micro l (females); CD8 T cells, 898/ micro l (males) and 716/ micro l (females); and CD4/CD8 T-cell ratio, 1.13 (males) and 1.41 (females). We concluded that (i) the WBC and hemoglobin values of healthy HIV-negative adults from the CAR are lower than the reference values currently used in the CAR and (ii) the absolute CD4 T-cell counts of healthy HIV-negative adults from the CAR are similar to values for Europeans but the absolute CD8 T-cell counts are much higher. Thus, the CD4/CD8 T-cell ratios for healthy adults from the CAR are significantly reduced compared to the ratios for healthy Europeans.