The glycaemic control of infants and of their mothers was studied at delivery and on day 7 after birth in 11 control and 20 insulin-dependent diabetic women. At delivery, venous blood glucose was lower in infants of diabetic mothers compared with control infants (p less than 0.02). Seven days after birth, no significant difference in blood glucose could be found between control and infants of diabetic mothers. C-peptide levels were higher in infants of diabetic mothers compared with control infants (p less than 0.01). On day 7 after birth, the C-peptide levels remained higher only in infants of Class B, C, D diabetic mothers. Glycosylated haemoglobin was lower in the venous blood of infants than of their mothers (p less than 0.001). Glycosylated haemoglobin was lower in control mothers than in diabetic mothers (p less than 0.05), but it was higher in the venous blood samples from control infants compared with infants of diabetic mothers at delivery (p less than 0.05) and 7 days after (p less than 0.01). At delivery infants' glycaemia and infants' glycosylated haemoglobin correlated (r = 0.44, p less than 0.02). C-Peptide and glycosylated haemoglobin levels in infants at delivery also correlated (r = -0.42, p less than 0.05).