Classical 3beta-hydroxysteroid dehydrogenase (3beta-HSD) deficiency is a rare cause of congenital adrenal hyperplasia. We report two sisters presenting with delayed diagnoses of classical 3beta-HSD, despite salt wasting (SW) episodes in infancy. Sibling 1 was referred for premature pubarche, slight growth acceleration, and advanced bone age, whereas sibling 2 had no signs of virilization. At referral, increased 17alpha-hydroxyprogesterone associated with premature pubarche at first suggested a nonclassical 21-hydroxylase deficiency. Sequencing of the CYP21 gene showed both girls only heterozygotes (V281L mutation). This result, combined with SW in infancy, suggested a 3beta-HSD deficiency because of increased dehydroepiandrosterone sulfate levels. Further hormonal studies showed markedly elevated Delta5-steroids, in particular 17alpha-hydroxypregnenolone greater than 100 nmol/liter (the clue to the diagnosis) and elevated Delta5-/Delta4-steroid ratios. Sequencing of the type II 3beta-HSD gene documented that both girls were compound heterozygotes for T181I and 1105delA mutations. Retrospectively, elevated levels of 17alpha-hydroxyprogesterone were found on blood spots from Guthrie's test. There is no previous report of the combination of SW and premature pubarche due to mutations in the type II 3beta-HSD gene. Because neonatal diagnosis could have prevented life-threatening crises in these girls, this report further supports the benefits for neonatal screening for congenital adrenal hyperplasia whatever the etiology.