Steroid hormones secreted by fetal adrenocortical cells are considered to be a requirement for a fetus to maintain intrauterine life, but, to date, the regulation of steroid hormone secretion has not been studied in detail in the human fetal adrenal gland. In this study, we examined the immunolocalization of steroidogenic enzymes and their local regulation, including adrenal 4-binding protein (Ad4BP or NR5A1), steroidogenic acute regulatory protein (StAR), P450 cholesterol side-chain cleavage (P450scc or CYP11A1), P450 17α-hydroxylase/17,20-lyase (P450c17 or CYP17), 3β-hydroxysteroid dehydrogenase/isomerase (3β-HSD), P450 21 hydroxylase (P450c21 or CYP21), dehydroepiandrosterone sulfotransferase (DHEA-ST), P450 oxidoreductase and cytochrome b5, in the human fetal adrenal gland (n=31) obtained from fetuses ranging in ages from 14 to 40 weeks of gestation. Ad4BP immunoreactivity was detected in all adrenocortical zones throughout gestation, suggesting that this nuclear protein is likely to be essential in the development of the human adrenal. Immunoreactivity for StAR, P450scc, P450c21, P450 oxidoreductase and cytochrome b5 was detected only in fetal and transitional zone between 14 and 22 weeks of gestation, but was detected in all three zones after 23 gestational weeks. 3β-HSD immunoreactivity was not detected in any of the three cortical zones prior to 22 weeks of gestation, but became discernible in the transitional zone and definitive zone after 23 weeks. Immunoreactivity for P450c17 and DHEA-ST was detected in the transitional and fetal zones throughout gestation, but not in the definitive zone. These results suggest that the human adrenal cortex may produce dehydroepiandrosterone (DHEA) in the transitional and fetal zones throughout gestation, and cortisol in the transitional zone after the 23rd week of gestation.