Although congenital adrenal hyperplasia due to 3β-hydroxysteroid dehydrogenase deficiency generally reveals a predominance of Δ⁵-3β-hydroxysteroids, on occasion substantial quantities of pregnanetriol have been found as well. It appears that the latter steroid more often occurs in the subjects who have survived beyond infancy. The use of the measurement of pregnanetriol alone may therefore not be relied upon as a sole determinant of the specific form of defective steroidal biogenesis. It is more characteristic of the 21-hydroxylase deficiency. However when both Δ⁵-pregnenetriol and pregnanetriol are measured the ratio of the former to the latter is always considerably below 1.0 in 21-hydroxylase deficiency and always above 1.0 in 3β-hydroxysteroid dehydrogenase. Furthermore, 11-ketopregnanetriol has been found only in the urine of subjects with the 21-hydroxylase deficiency. Thus, these two forms of defective steroidal biogenesis may be distinguished by the measurement of these three urinary steroidal metabolites.