A prospective study of 1238 full-term Chinese newborn infants was conducted to determine the incidence of neonatal jaundice and associated factors. A significantly more severe degree of hyperbilirubinaemia was present in infants whose ABO blood group was incompatible with that of their mothers and those who were deficient in the enzyme glucose-6-phosphate dehydrogenase (G6PD). Among the remainder, clinical jaundice was present in 87% and 23.9% had a peak serum bilirubin (SB) concentration greater than 204 mumol/l. Factors that were found to have an association with a higher peak SB concentration included: male infants; elder siblings who had a history of neonatal jaundice; and breast-fed infants with or without supplementation with formula feed. Factors that were found to have no significant association with the peak SB concentration were: gestational age; birthweight; the mode of delivery of the infants; maternal consumption of Chinese herbs and syntocinon induction or augmentation of labour.