Serum concentrations of dehydroepiandrosterone (DHA), DHA sulfate, and cortisol were measured in 52 chimpanzees (aged 0.5--10 yr), 76 Macaca mulatta (aged 0.25--5 yr), and 80 Macaca nemestrina (aged 0.5--9 yr). Sexual maturation was assessed by age and by the presence of menarche or the appearance of perineal turgescence in the females and by measurement of serum testosterone in the males. In an additional group of 10 young adult female M. mulatta, four repeated determinations of these same steroids at 30-min intervals demonstrated that the stress of capture and venipuncture caused a significant rise in serum levels of not only cortisol but also of DHA and DHA sulfate. The chimpanzees demonstrated an age-related rise in serum concentrations of DHA and DHA sulfate relative to cortisol which began before the onset of puberty and thus closely resembled human adrenarche. In M. mulatta, serum DHA levels showed no change with age, while DHA sulfate values decreased progressively both before and during puberty. The pattern in M. nemestrina was similar, with stable DHA and declining DHA sulfate levels before and during puberty. However, in the oldest group (aged 6--9 yr) of mature M. nemestrina, there was a significant postpubertal rise of both DHA and DHA sulfate with no change in serum cortisol. These data suggest that monkeys, just as higher primates, may show increasing adrenal secretion of C19 steroids at around 6--9 yr. This adrenarchal process appears to be completely independent of sexual maturation and probably merely reflects the influence of progressive adrenal growth and the resulting impact of changing intraadrenal steroid concentrations upon steroidogenesis in the zona reticularis.