Alloimmune neonatal neutropenia (ANN) is reported for the first time in two Australian aboriginals. Both infants displayed the typical clinical features of ANN with profound neutropenia which persisted for 7 weeks and only minor infectious episodes. However, management strategies differed for the two infants because in one case (complicated by uncertain paternity) serological confirmation of ANN was not obtained until after recovery of the infant's neutrophil count. The maternal antibodies could not be assigned to known neutrophil antigen specificities and a new antigen may be involved. The antibodies were reactive with > 99% of neutrophils in a Caucasian population. Aboriginals comprise 1% of the total population of Australia and 1-2% of the obstetric population at our institution. Thus, ANN may be an unrecognized disorder in this ethnic group and a possible cause of neonatal infection and mortality.