The urinary concentrations of dopamine, noradrenaline and adrenaline were measured by a radioenzymatic method in 212 full-term and premature newborns. The ranges, means and standard deviations from birth to 4 days + are presented. The excretion of dopamine was ten times that of noradrenaline or adrenaline. The absolute concentrations of each catecholamine were reduced as birth weight decreased. The values were increased in babies with fetal distress. Any changes found in hypoglycaemic or jaundiced infants were attributable to prematurity. Very high levels were found in a few infants given tolazoline. We speculate that the role of dopamine production and excretion in the newborn has been underestimated. Dopamine may have an important role to play in the homeostatic mechanisms of the newborn.