We assessed the activity of the sympathoadrenal system in infants of diabetic mothers. Concentrations of metanephrine in the amniotic fluid were correlated to amniotic fluid lung profiles. At the time of delivery, the levels of umbilical artery and vein plasma catecholamines were compared to the incidence of neonatal complications. Mature lung profiles correlated significantly with progressively rising metanephrine concentrations. Infants who had a higher incidence of neonatal complications at delivery had significantly higher plasma catecholamine levels as well. It is concluded that in infants of diabetic mothers there is a higher significant association between the sympathoadrenal activity and lung maturation. The majority of infants of diabetic mothers have excessive sympathoadrenal activity at birth, which could potentially lead toward catecholamine depletion and related complications in the first days of life.