Concentrations of unconjugated dehydroepiandrosterone, estradiol, and estriol were measured in samples of amniotic fluid from uneventful pregnancies of 9-40 weeks conceptual age. There was no apparent influence of fetal sex upon the levels of these steroids. Dehydroepiandrosterone concentrations rose slightly from 9-20 weeks, and then showed little further change. Estradiol concentrations declined slightly from 9-20 weeks; after 32 weeks gestation, there was a 2-fold rise to term. Estriol levels rose in almost exponential fashion throughout gestation.