Total plasma carnitine was analysed in 19 women, with uncomplicated pregnancies, who underwent elective caesarean section, and in their neonates. The women were given a balanced glucose (glucose group) or saline (saline group) infusion, group allocation being on a random basis. The carnitine levels in maternal or infant plasma did not differ between these two groups. At delivery, the mean maternal carnitine value, 17.4 +/- 1.25 mumol/l, was lower than the mean infant value, 25.9 mumol/l +/- 2.67 (mean +/- SE, p less than 0.005) and lower than the mean value in non-pregnant, fertile women, i.e. 40.9 +/- 1.22 mumol/l. The mean carnitine value in the unfed neonate had not changed when the infant was 4 hours old. A positive correlation was found between carnitine levels in maternal and infant plasma (p less than 0.01). At delivery, the levels of non-esterified fatty acids and 3-OH-butyrate in infant plasma were different in the two groups, but not at 4 hours of age. The results suggest that the maternal carnitine level is the most important factor governing plasma carnitine levels in the neonate.