Plasma levels of dehydroepiandrosterone sulfate (DHAS) were measured in 513 normal full term newborns, infants, children, adolescents, and adults and the results were expressed in micrograms per dl. In infancy and childhood, DHAS levels were similar in both sexes. In 74 neonates, mixed cord blood mean values /+- SD were 134.6 +/- 64. During the first day of life, plasma DHAS levels were 140 +/- 125 in 33 neonates. During the first month of life, DHAS decreased drastically, then more progressively until the 6th month of life. Between 1-6 months of age, mean levels were 5.9 +/- 4.7 in 40 children. DHAS was very low between 1-6 yr of life (2.3 +/- 1.6) and rose abruptly at the 7th year of life. Thereafter, DHAS continued to increase correlatively with age and pubertal stages in both sexes, a further increase after age 16 or pubertal stage P5 was noted only in male subjects. In adults, DHAS was significantly higher in male (224 +/- 93) than in female (138.3 +/- 51) subjects. DHAS levels were compared to those of dehydroepiandrosterone; at two periods of life, early infancy and adulthood, their patterns differed. After long term hCG stimulation, DHAS increased significantly in 45 normal prepubertal boys and in 2 boys with adrenal insufficiency. These data would suggest a direct testicular production of DHAS.