During normal human sexual development the adrenal gland undergoes a maturational process, termed adrenarche, which results in increased adrenal secretion of androgens and estrogens. Adrenarche begins several years before the onset of gonadal maturation and correlates with the appearance of the adrenal reticular zone. In normal puberty, adrenarche and gonadarche (gonadal maturation) are closely linked, but in pathological situations adrenarche can occur without gonadarche, and gonadarche without adrenarche. Although the onset of puberty can be accelerated by elevated levels of adrenal androgens in patients with congenital adrenal hyperplasia, a normal onset of puberty in patients with premature adrenarche and primary adrenal insufficiency suggests that physiological levels of adrenal androgens do not exert a major influence on the timing of pubertal onset. Adrenal androgen levels and their developmental patterns differ markedly among species and, of the species so far examined, only the chimpanzee exhibits an adrenarche similar to that of man. Despite considerable investigation, the mechanisms underlying the initiation and maintenance of adrenarche are unknown.