Adrenarche is the puberty of the adrenal gland. The descriptive term "pubarche" indicates the appearance of pubic hair, which may be accompanied by axillary hair. This process is considered premature if it occurs before age 8 yr in girls and 9 yr in boys. The chief hormonal products of adrenarche are DHEA and DHEAS. The well-documented evolution of adrenarche in primates and men is incompatible with either a neutral or harmful role for DHEA and implies most likely a positive role for some aspects of young adult pubertal maturation and developmental maturation. Premature adrenarche has no adverse effects on the onset and progression of gonadarche and/or final height. Mechanisms for initiation of adrenal androgen secretion at adrenarche are still not well understood. Maturational increases in 17-hydroxylase and 17,20-lyase are seen together with a lower activity of 3beta-hydroxysteroid dehydrogenase (3beta-HSD). There is good evidence that the zona reticularis is the source of adrenal androgens. Adrenarche and gonadarche are regulated differently. Although premature adrenarche has been thought to be a benign, normal variant of puberty, our findings indicate that, for certain girls, premature adrenarche represents an early clinical feature of syndrome X (obesity, hypertension, dyslipidemia, insulin resistance). Perhaps the early identification of these patients will permit early therapy, such as lifestyle changes, including dietary and activity level intervention. As insulin resistance is an underlying feature of premature adrenarche, it seems rational to assess the efficacy and safety of using insulin-sensitizing agents to treat these individuals. In the absence of controlled longitudinal studies, the cross-sectional data available from our studies suggest that premature pubarche driven by premature adrenarche and hyperinsulinemia may precede the development of ovarian hyperandrogenism, and this sequence may have an early origin with low birth weight serving as a marker. Premature adrenarche may thus be a forerunner of syndrome X in some girls.