Summary. Serum samples from 116 women taken at different times during and after the first pregnancy were tested for the presence of cytotoxic lcucocytc antibodies against the husbands' Ieucocytes. Antibodies were found in the serum of 15 women, 11 times during the pregnancy, and as early as at 24 weeks of gestation. All antibodies examined were IgG, even the earliest detectable antibodies. All sera contained antibodies against antigens common to granulocytes and lymphocytes; four sera also contained granulocytespecific antibodies and none lymphocyte‐specific antibodies. No antibodies were demonstrable in any of the cord‐blood and no granulo‐ or lympliopenia was seen in any of the children. © 1969 Blackwell Publishing Ltd