Abstract.A family is presented, in which the mother developed strong neutrophil granulocyte‐specific antibodies with the specificity anti‐NA1. The first and third children, both NA1‐positive, suffered from severe transient neonatal neutropenia, but the second child, NA1‐negative, did not.Anti‐NA1antibodies were detectable in the serum of one affected child and the antibody level was directly related to the extent of neutropenia. The incidence of granulocyte‐specific antibodies in 198 pregnant women was determined and foun