109 Nigerian neonates with serum bilirubin of 12 mg% and above, who presented at the Children's Emergency Room of the University College Hospital, Ibadan between November 1980 and February 1981 were investigated for bacterial sepsis and other causes of hyperbilirubinaemia. A detailed history of exposure to drugs likely to be icterogenic was also taken. Of the 109 infants, 67 (62%) were G6PD deficient and 41 (67%) of the latter had no obvious cause for the precipitation of jaundice. However 106 (97%) of the jaundiced infants had been exposed to agents capable of causing haemolysis in G6PD deficiency; 24 (22%) had bacteriologically proven septicaemia and in only five (4.6%) was sepsis the sole cause of hyperbilirubinaemia. There was no significant differences in the frequency of bacteriologically proven sepsis between the infants with normal or deficient G6PD status. Septicaemia however significantly increased the severity of jaundice among G6PD deficient infants. This study suggests that infection is common in severely jaundiced Nigerian infants and there is a need to reassess the role of exogenous agents in the pathogenesis of neonatal hyperbilirubinaemia in our community.