Human and animal studies suggest impaired central nervous system (CNS) development due to corticoid use in the perinatal period. In this study, hydrocortisone was given to pregnant rats and the development of the fetal dopamine (DA) and norepinephrine (NE) systems in the CNS was investigated. In the fetal rat brain DA and NE systems develop between days 12 and 17 of gestation. Hydrocortisone (HC), 57 mg/kg/day, or saline (SAL) was given intraperitoneally at day 12 or 15 of gestation. The offspring were studied at days 20 to 21 of gestation and days 12 to 13 in the neonatal period. Brain amine systems were visualized using a modified cryostat glyoxylic acid histofluorescence method, and DA and NE levels were determined in whole brains by means of a radioenzymatic assay. The visualized amine systems were evaluated semiquantitatively for distribution and fluorescence intensity without previous knowledge of the administered drug. The amine systems of the HC and SAL groups showed an equal maturation. In both groups cell bodies were demonstrable in areas A1 to A13 and axon terminals in all examined final regions. The distribution and the fluorescence intensity did not show consistent differences for the HC and SAL brains. The concentrations of DA and NE were similar in the offspring of the SAL- and HC-treated animals. The results indicate that HC given during pregnancy does not influence the proliferation of amine cell bodies or the arrival of axon terminals in the regions where the synapses form.