Pregnant HS/Ibg mice received 3 g/kg phenobarbital in their milled food; control dams received unadulterated milled food. Their offspring were tested on ages 22 and 50 days for norepinephrine (NE) and dopamine (DA) levels and DA turnover in the hypothalamus and striatum. Additional groups were tested on days 8, 22, and 50 for brain stem tryptophan hydroxylase (TPH) activity. Hypothalamic DA level among offspring with prenatal PhB exposure (B offspring) was 37% below control level on age 22 days and 61% below control on day 50 (p less than 0.001). Hypothalamic NE level of B offspring was reduced on age 50 days (52%, p less than 0.05) and not on day 22. DOPAC level and DA turnover did not differ among B and control groups. Prenatal exposure to PhB did not have a significant effect on TPH activity. The changes in catecholamines may mediate, at least in part, some of the early barbiturate induced neuromorphological and behavioral changes previously found in our laboratory.