To elucidate how often the presence of leucocyte antibody in the serum of a pregnant woman will lead to the development of neonatal clinically significant neutropenia in her child, a group of 44 infants, all borne by mothers with leucocyte antibody in their sera, were followed over their first three months of life by means of clinical and haematological investigations. At the clinical investigations the infants presented no conspicuous deviations from normal, especially no particularly high frequency of infections was found.At the haematological investigations, the first of which was not performed, however, until the infants were two weeks old, no reduced mean counts of leucocytes or granulocytes were found in the group. No single case of neutropenia or granulocytopenia was found, and in particular the infants with infectious diseases presented none of these symptoms.Since the study shows that neonatal neutropenia with severe infectious disease does not usually develop in cases with materno‐foetal leucocyte incompatibility, the authors suggest that the cases of neonatal neutropenia associated with maternal leucocyte antibody reported in the literature might be accounted for by a coincidence of the two phenomena.Furthermore, the results of the leucocyte‐immunological investigations performed are discussed, particularly with a view to the relationship between the leucocyte antibody conditions in the mother and her offspring.This study was supported by grants from The Danish State Research Foundation (Statens almindelige Videnskabsfond) and The Foundation in Aid of Medical Science (Fonden til Lægevidenskabens Fre