A controlled study was conducted to assess the role of high-dose i.v. immunoglobulin (HDIVIG) therapy in neonatal immune haemolytic jaundice. Patients with ABO and/or Rh incompatibilities proved by significant hyperbilirubinaemia (>204 mmol l(-1)), positive direct antiglobulin test and high reticulocyte count (> or =10%) were randomly assigned to receive either conventional phototherapy alone or phototherapy with high-dose i.v. immunoglobulin (1 g kg(-1), over 4 h) as soon as the diagnosis was established. Exchange transfusions were performed if serum bilirubin concentrations exceeded 290 mmol l(-1) and increased by more than 17 mmol l(-1) per h despite both treatment manoeuvres. Eight of 58 patients in the HDIVIG group required exchange transfusions, whereas it became necessary in 22 of 58 patients in the control group (p<0.001). The durations of phototherapy and hospitalization in terms of hours were significantly shorter in the HDIVIG group (p<0.05). No side effects of HDIVIG therapy were observed. In conclusion, HDIVIG therapy in newborns with ABO or Rh haemolytic diseases reduces haemolysis, serum bilirubin levels and the need for blood exchange transfusion, a procedure which has potential complications and carries a risk of mortality.