Pregnanetriol was not excreted by an infant (7 days old) who was later shown to have a defect in steroid 21-hydroxylase. However, the excretion of this compound increased during the following days (1.2 mg on the thirteenth day of life). A high excretion of 3β-hydroxy-Δ steroids was the most noticeable abnormality in steroid excretion noted on the seventh day of life (e.g., 3β, 16α-dihydroxy-5-pregnen-20-one, 15 mg; 3β, 21-dihydroxy-5-pregnen-20-one, 1.4 mg and 3β, 16α-dihydroxy-5-androsten-17-one, 7.4 mg). This high 3β-hydroxy-Δ steroid excretion results in difficulties in distinguishing a defect in 3β-hydroxy steroid dehydrogenase from a 21-hydroxylase deficiency. At the age of 14 months the principal steroids excreted were those predominant in other cases of 21-hydroxylase deficiency, viz. pregnanetriol and 5β-pregnane-3α, 17α, 20α-triol-11-one (11-oxo-pregnanetriol).