EDTA-treated blood samples from rhesus macaques were collected and stained (group 2; Table II) 1, 4, 7, 10, and 14 days after iv BrdU administration. The BrdU+ cell fraction, half-life, and daily production were measured and calculated respectively for neutrophils (A, D, H), basophils (B, E, G), and classical monocytes (C, F, I). Blood kinetics were expressed as the mean ± SD of the BrdU+ cell fraction for each age group. Nonparametric Spearman correlation tests were used to compare half-life and daily production of cell types against age of the animals. P < 0.05 was considered statistically significant.