The occurrence of nonclassical congenital adrenal hyperplasia among children with precocious pubarche is still a matter of debate. We studied the adrenal steroid response to ACTH stimulus (Synacthen, 0.25 mg i.v. bolus) in 26 Italian children (5 boys, 21 girls) who had presented pubic hair, without other signs of virilization, at ages ranging between 0.45 and 8.8 years. The control groups comprised 8 prepubertal children (5 boys, 3 girls) and 12 children at Tanner stage 2 for pubic hair development (1 boy, 11 girls). Two patients were diagnosed as having nonclassical congenital adrenal hyperplasia: 1 due to 21-hydroxylase deficiency, the other due to 3β-hydroxysteroid-dehydrogenase deficiency. The remainder, classified as having idiopathic precocious pubarche (PP), had adrenal androgens higher than normal prepubertal children and similar levels to those observed in early pubertal controls. In contrast to a recent report, we confirmed that mild adrenal enzymatic defects can occur in PP, and, consequently, the use of ACTH testing in children with PP seems to be recommended.