A review of the present knowledge of transplacental transmission of antineutrophil antibodies is given. A family in which one, possibly two of the three children had severe neutropenia after birth with subsequent infections, is described. An agglutinating antibody, directed against the neutrophil-specific antigen NA 1, was demonstrated in the maternal serum. The father and all three children were NA 1-positive. This case is another example of isoimmune neonatal neutropenia due to anti-NA 1 antibodies.