The steroids in faeces from infants less than one year of age have been studied. Two fractions, monosulphates and “diconjugates”, were separated by chromatography on Sephadex LH‐20. The steroids were liberated by solvolysis and were studied by thin‐layer chromatography and gas‐liquid chromatography‐mass spectrometry. Eighteen steroids, most of them having a 3β,16‐dihydroxy‐Δ5 structure, were identified in the monosulphate fraction of pooled faeces from infants 1–4 months of age. Of these, androst‐5‐ene‐3β,16β,17α(and)17β‐triols, 3β‐hydroxypregna‐5,16‐dien‐20‐one, 3β,16β‐dihydroxypregn‐5‐en‐20‐one, 3α,16α‐dihydroxy‐5β‐pregnan‐20‐one, pregn‐5‐ene‐3β,16α,20α‐triol, pregn‐5‐ene‐3β,20α,21‐triol and pregn‐5‐ene‐3β,16α,20α,21‐tetrol have not been reported as occurring in urine from infants. In addition, eight steroids were found, the stereochemistry of which was not confirmed. Four of the 16‐hydroxylated steroids were also present in the “Diconjugate” fraction. In contrast to faeces from the younger infants, pooled faeces from infants 6–12 months of age contained only small amounts of steroids, mainly pregn‐5‐ene‐3β,20α‐diol and pregn‐5‐ene‐3β,17α,20α‐triol. The results indicate that significant amounts of steroids are excreted in faeces during the first few months of life, and that metabolism of these steroids by the intestinal flora is of minor importance in this period. Copyright © 1969, Wiley Blackwell. All rights reserved