Aim: To determine the incidence amongst infants born at term or near-term of extreme hyperbilirubinaemia, i. e. , with a serum concentration of unconjugated bilirubin exceeding the limit above which an exchange transfusion was indicated according to the authorized guidelines. Method: The investigation period covered 2 y, 1 January 2000 to 31 December 2001, and included all infants born alive at term or near-term in Denmark. All infants with extreme hyperbilirubinaemia admitted to paediatric departments were recorded. Results: Thirty-two infants developed extreme hyperbilirubinaemia, i. e. , an incidence of 25 per 100 000. The maximum total serum bilirubin concentration (TSB) was 492 (385-689) μmol/l (median (range)). The median value of the exchange transfusion limits was 450 μmol/l. Twelve infants had signs and symptoms of central nervous system involvement; 11 had acute bilirubin encephalopathy phase-1 symptoms; and one had phase-2 symptoms. Nineteen infants developed extreme hyperbilirubinaemia during primary admission to the maternity ward or neonatal department; the others after having been discharged. There was no difference in maximum TSB between those infants not discharged from hospital and those infants admitted to hospital from home. Maximum TSB appeared latest amongst those infants admitted from home (p < 0.01), and these more often had signs and symptoms of central nervous system involvement (p < 0.05). Ten infants were of non-Caucasian extraction. Less than half of all Danish mothers receive both verbal and written information after birth on jaundice in the infant. Conclusion: Twenty-five per 100 000 infants born at term or near-term developed extreme hyperbilirubinaemia, the majority of them whilst in hospital. Infants admitted from home more often had signs and symptoms of central system involvement. Aim: To determine the incidence amongst infants born at term or near-term of extreme hyperbilirubinaemia, ie, with a serum concentration of unconjugated bilirubin exceeding the limit above which an exchange transfusion was indicated according to the authorized guidelines. Method: The investigation period covered 2 y, 1 January 2000 to 31 December 2001, and included all infants born alive at term or near-term in Denmark. All infants with extreme hyperbilirubinaemia admitted to pediatric departments were recorded. Results: Thirty-two infants developed extreme hyperbilirubinaemia, ie, The maximum total serum bilirubin concentration (TSB) was 492 (385-689) μmol / l (median range). The median value of the exchange transfusion limits was 450 μmol / l. Twelve infants had signs and symptoms of central nervous system involvement; 11 had acute bilirubin encephalopathy phase-1 symptoms; and one had phase-2 symptoms. Nineteen infants developed extreme hyper the was later after those infants admitted From home (p <0.01), and these more often had signs and symptoms of central nervous system involvement (p <0.05). Ten infants were of non-Caucasian extraction. Less than half of all Danish mothers receive both verbal and written information after Birth on jaundice in the infant. Conclusion: Twenty-five per 100 000 infants born at term or near-term developed extreme hyperbilirubinaemia, the majority of them whilst in hospital. Infants admitted from home more often had signs and symptoms of central system involvement.